Thursday, March 29, 2012


My son participated in his third-grade Science Expo last week. Each third-grader was given a blank piece of cardboard and a stapled set of instructions. Students were to come up with their own questions, which they could answer by performing experiments, researching a topic, or giving a demonstration. They then would present their projects in a big poster session in the gym, where parents, teachers, and the other grades could walk through the rows of kids and ask about their work.

The Boy’s project came out of a short video I stumbled across in the usual Internet way of a guy out on his deck dropping magnets down a copper pipe. Like any good magician, he shows his audience the two pieces separately, and then performs the trick, exploding all expectations in the process. The magnet doesn’t stick to the pipe but instead tumbles softly down into his hand.  When it came time for The Boy to settle on his topic, he remembered the video right away and wanted to go looking for the explanation.

The short clip gave us a couple of leads — neodymium, eddy currents — so that’s where we started. The magnets were easy to get off the Internet, arriving in a couple of days in a clear plastic tube wrapped in warnings. The pipe was a lot less easy to come by, oddly enough. Lots of places in town would sell us a contractor’s standard ten-foot length, but we only wanted a foot or so. After much walking and asking around, we finally found a hardware supply in Chinatown with a manager who happily opened one of his own pipe-cutter packages to accommodate us.

Once outfitted, we went for replication. Would our own neodymium magnet float down our own copper tube? Check. Even having seen the video, The Boy and I found the result hypnotic, the pleasant clink of metal on metal, the lazy drift of the stack of magnets down into his waiting palm.

Explanations pair with questions, and The Boy compiled a list of them to answer in his presentation, including:
  • Why doesn’t the magnet stick to the copper tube?
  • Why does the magnet float down the tube?
  • Does the tube have to be made of copper for the magnet to float?
  • What is an eddy current?
The idea was that he would answer these questions on his poster, include a diagram picturing what’s going on that can’t be seen, and finish with a list of Fun Facts* about magnets.

We guided him a bit, but he did most of the heavy lifting research wise. Finding information for this kind of thing used to be difficult, but now the difficulty lies in sorting and understanding information. We googled magnet- and eddy-current-related phrases and turned up all sorts of videos and cryptic equations, along with pages of physics and industrial applications, and a few fairly simple explanations. The Boy took notes. We also actually went to our local library (nostalgia!) for age-appropriate books on magnets and magnet experiments, which proved to be a mother lode of Fun Facts.

You may very well be curious about answers to The Boy’s great questions, and though I don’t have my son’s showmanship, I’m happy to oblige with grade-appropriate answers. First off, copper is not ferritic, which means magnets aren’t attracted to it. But copper is an outstanding conductor, and that’s important here. A magnetic field moving through a conductor causes electric currents called eddy currents. All electric currents have their own magnetic fields.  So gravity pulling a strong magnet (in this case, four 1” x 1/8” neodymium stacked) down the conductor triggers eddy currents, which have their own magnetic fields that repel that falling magnet, just as the same poles of any two magnets repel. The eddy currents and their magnetic fields prove fairly weak (again, in this case), which means the magnet’s progress is only impeded and not arrested altogether.

Cool, right?

The Boy insisted (before we could) on writing the text of the poster himself, first translating his notes into an explanation on paper, and then typing everything up to be printed. We spent some serious time in font selection. My lovely wife helped him with the big center diagram, though it was his idea to have a foil-wrapped magnet popup in the center. He was proud of his work, and he had good right to be.

The day of the Expo, he carried his equipment and excitement to the gym himself. It opened to parents shortly after the morning bell rang, and my lovely wife and I flooded in with all the others to check everything out. We went by The Boy first, of course, and he was all set up and ready to perplex passersby with his “Magnet Mystery” (his poster’s title). He performed his demonstration for us just as he’d practiced — first asking what we thought would happen when he dropped the magnet down the copper tube, then asking for predictions about the same magnet going down a cardboard tube, then explaining all the forces at work that confounded those predictions. Q soon came by with a pack of her classmates (all grades visited throughout the day) to listen to her brother, and he enjoyed the audience. He was truly great.**

As were so many of the kids. We know lots of families now, and we took our time hearing The Boy’s friends tell us about mass and gravity, geysers, rainbows, penguins, great white sharks, milk carton turbines, and on and on. The girl set up right next to The Boy talked through a truly unsettling experiment on the effectiveness of soap v hand sanitizer, one that involved a UV flashlight that revealed the dirt on your hands right then and there. For my part, I managed to discomfit a kid with a nice display on color vision by asking her since different creatures have different color experience what she thought the real colors were.  “I dunno,” she said, looking up the aisle and anywhere else but at me.  Sometimes I wonder why I don’t end up eating all my meals alone.

Aristotle writes that all persons by nature desire to know.*** It can be an oppressive statement if you think about it — the need to explain nagging and persistent, like an itch. And there’s so much to be known. Spring bloomed suddenly, some afternoons have been pushing 70º already, and the early warmth and wet air have produced glorious morning fog.  Fog occurs when the ambient air reaches saturation, forming water droplets that reflect light, limiting visibility to at least 5/8 mile.  Copper: Chemical element name Cu; Atomic Number: 29; melting point: 1356.15K.  Celestial bodies lie in space like balls on a rubber sheet, curving space and time around them.  The body a machine, describable and flawed.  A second is equal to the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. Consciousness is an instance of consciousness of. F = ma, except when it doesn’t.  The Boy is an isotope of my wife and I; the recipe for his making written in a billion proteins.  Q hums sweetly while brushing her teeth (though she’ll deny it) — this a fact like any other.

Anyhow, thanks to The Boy, at least one mystery is explained enough.

*Nearly every third grader’s poster included Fun Facts, where “Fun” means something like Related But Random and Interesting.  The science teacher probably suggested including them as a way to fill white space, which, given that this is likely the first public opportunity these kids had to present a poster, must have seemed positively Antarctic to most of them.
**Dare I say he was magnetic? I do dare say so, at least in a footnote.
***The opening line of his Metaphysics, usually translated as all men desire to know, but he’s dead enough to be forgiven this oversight. Also, perhaps no one better encapsulated this desire than Aristotle himself.

Friday, March 16, 2012

Body shop

I start my 22nd session of physical therapy, as I’ve started the 21 others, by paying upfront.  I pretty much have myself and pickup basketball to blame for my broken wrist and the surgery to right it, but many people coming here to come back from their injuries are in the middle of legally faulting someone else, and who knows when those suits will result in costs being covered, so they insist.

After I put the receipt with the others, I hang up my coat in the odd little closet* and go back to whichever of their two rooms has an open seat. This office specializes in hands, arms, and shoulders, and it’s nearly full, as always. Most people spend many weeks in physical therapy, and I recognize almost everyone. The Belgian high-school girl who hurt her finger playing varsity volleyball pokes neon-colored putty to work her grip. The two female cops sit together as usual, cracking each other up with cop-speak jokes and comparing workman’s comp attorneys. The young guy with two phones comes later, talking to a series of people while a therapist sends electricity through a muscle in his forearm. I haven’t seen the woman with the plastic-surgeon dad in a while, probably since she can get cortisone shots at will.  Once, after I had become a regular, I actually found myself saying to a stranger next to me whose shoulder was being unbandaged: “What are you in for?”

I find a place in the room where each seat has a wooden TV-dinner tray next to it, rickety as the limbs leaning on it, and with the obligatory lithograph of Eschers hands drawing each other to life, which almost makes literal sense given its context. The other room has old elementary-school desks for tables and a framed closeup from Michelangelo’s Sistene Chapel ceiling, the really famous part where God reaches out to Adam’s limp (injured?) hand. The entire place has an oppressive level of metaphor density.** The woman who works me over twice a week asks how my wrist feels, and I say “fine” because, like all questions of this sort, its answer is pure ornament. She’s good at juggling patients, has to be, and she lays a big blue bag of heat on my hand to loosen it up and returns to someone else in the other room.

Sessions are like getting your hair cut, only your hair is broken and it hurts. My therapist and I have been through so much small talk in two months that I have a fuller picture of her than most of my coworkers and neighbors. I know that she plays mahjong with her friends twice a month and that she picked up the game pretty quickly from her grandmother. I know that her husband is finishing up his MBA and has an enviable ease with foreign languages. (I know that his grandmother is a surly Holocaust survivor.)  They’re childless but thinking sometime maybe eventually. She’s left handed and is forever after whoever borrowed her special scissors. I know where she and her husband are each from originally and what they’ve done more or less every weekend for the last two-and-a-half months — something I no longer know about myself.

After she returns and removes the heat, I do some wrist curls with a 5 lb. weight, then squeeze an old gripper thing 30 times. Once I’ve limbered*** up a bit, my therapist bends my wrist. Hard. We do what she gamely calls a “strong stretch” that usually involves me looking away and down from the hurt while she applies her full body weight to my hand and aims for 90º flexion. I try the Zen thing of detaching myself from the material experience. I cycle through pictures in my head. My arm as cold dough that grows more pliable as its folded and rolled. A car door iced shut overnight finally coming free. An iron bar glowing orange on an anvil, throwing sparks at each hit, but taking shape. The Tin Man choked with rust, already with a heart but needing oil and an adventure to discover it.

The idea of physical or occupational therapy, the purpose, arises out of the fact that adults cannot be trusted to properly harm themselves after injury. Expertise is involved, too, of course — bodies can break in so many ways.**** Each of the three times the cast came off my son’s arm, he was unleashed back onto the baseball field and into the schoolyard and the swimming pool, without need for therapy. His body is a riot of growth, which helps with recovery from just about anything, and he (like most kids) can easily forget hurt. Adults, though, generally have vivid memories of pain and tend to convert it and anticipation of it into suffering. We quickly restrict or retire hurt limbs, which in turn leads our bodies to slowly give up on them. After I hurt my wrist back in May, I wrapped and iced and defended it for several weeks to give it time to heal itself, but time instead eroded my range of motion. And then the surgery and the pins and surgical screw and the nine-week cast all conspired to fix my hand straight.  Now it has to be bent further than I want it to if I want to come back.

The Zen thing doesn’t work. My wrist pops and smarts like hell but won’t stay past my best angle reached a few weeks ago. My PT reminds me, again, of how I came in, with flexion and extension of basically 0º, to make me feel better about where I can get to now, which is 50º and 60º respectively. It occurs to me that the old saying really should go, “Time fixes all wounds,” with ‘fix’ smuggling in all its senses.

All the effort going on in rooms makes them stuffy, and my PT cracks the window near my seat.  The days have gotten glorious, and I’m glad to welcome in the loud warm air of 57th Street. I think of Q and her classmates running in the schoolyard, waiting in the 60° morning for the bell, how they shed their coats and become their bodies.

We’re all done, she says.  See you next week.

*I’m fascinated by this closet, possibly unhealthily so. It seems to contain roughly twice the space of the waiting room it’s off of, and its bar is stocked with weirdly thick hangers, like bunch of taupe hotdogs bent into triangles.
**Example: The Michelangelo print is even from before the restoration, meaning it has visible cracks running across the arms of both God and Adam.
***One thing I learned while writing this: The word ‘limber’ does not, lexicographers apparently think, share the same origin as the word ‘limb’. According to The Oxford English Dictionary, ‘limb’ can be traced back to Old English’s lim, which means strong. The OED says that ‘limber’ probably entered the language much later (around the 16th or 17th century) and may have the word ‘limp’ as an ancestor. I know, right?
****The Wikipedia page on “physical therapy” makes for good reading. Assuming what’s there is mainly true, PTs in the U.S. were first called “reconstructive aides.” It says that the first American PT school was at Walter Reed Army Hospital in response to injuries incurred during World War I, and the first professional organization, founded in 1921, was called the “American Women’s Physical Therapy Association.” Though this approach to convalescence can be traced back to Hippocrates, modern physical therapy cut its teeth on war and polio, and was almost exclusively performed by women.

Friday, March 02, 2012

Data dumped on

(Photo by The Gates Foundation used under CC license)

I like to think the best of people. I try to start with the assumption that everyone believes, honestly, in what she considers good reasons for something, even if that something and those reasons turn out to be misguided about something extremely important.

The New York City Department of Education recently released performance rankings for 18,000 New York City public school teachers. In the New York Times’s summary: “The reports, which name teachers as well as their schools, rank teachers based on their students’ gains on the state’s math and English exams over five years and up until the 2009-10 school year.” In the report, each teacher (or set of teachers) receives a percentile ranking indicating whether the teacher is Low (0-5%), Below Average (6-25%), Average (25-75%), Above Average (75-95%), and High (95-100%).

Everyone pretty much agrees by now (or should at any rate) that performance on standardized tests reveals precious little about individual students and even less about their teachers. Here’s a simple example: Scores on a single test may be indicative of academic level (and, more tenuously, of teacher competence), but such scores may better represent inadequate breakfasts, wrong sides of beds gotten up on, bad pencil luck, and on and on and on. Not to mention the deep and abiding structural walls/ramps of economic strata and cultural pressures of family and community. Average scores may also vary widely across classes because, for very real example, one teacher’s students arrived day one better prepared than the other and therefore test as such. A teacher with the lower average score could in fact be “adding more value”* than his colleagues — his students could have scored far better due to his instruction than they would have without it, even if they ultimately scored lower than fourth graders a door or county over. In sum, standardized test scores could easily be the result of a galaxy of external factors that have nothing whatsoever to do with teacher potential and performance, which means they make an exceedingly poor metric for evaluating teachers in any real way.

At this point one could just jettison the whole project of trying to judge teachers (and perhaps even students) via standardized test scores, or one could try to evaluate the scores in a more sophisticated way. The NYC DOE and other places have gone for the latter, calculating the very personal percentages dumped last week via what’s called a “Value Added Model” (VAM). VAMs more generally are mathematical models designed to factor in (and therefore factor out) the swarm of influences on students to isolate the contribution of the teacher to student performance, thereby giving the “value added” by the instructor. A very (very) simple version of this is having students take an exam early on in the year to serve as benchmarks, testing them again later in the year, and then comparing scores to gauge improvement. VAMs try to account for all sorts of external factors so that the internal cause of student performance (viz., teaching) can be revealed. (For a great and extremely accessible primer on VAMs, see a paper by John Ewing in the May 2011 Notices of the American Mathematics Society.)

Not a bad idea if it works — this is me still trying to think the best of everybody — but it’s not at all clear that it does. As some have pointed out, the data collected is shot through with errors, from mis-attributed test scores to altogether absent data to sample sizes to small for the statistics they support (classes of 10 students, etc.). These kinds of error can perhaps be avoided with tighter reporting, assuming public schools have the funds and personnel to dedicate to that sort of thing.** The more troubling inaccuracy, though, is with the VAM itself. As you can tell from the examples just two paragraphs back, the factors contributing to student preparation and success prove exceedingly complex and quickly vexatious. The accuracy of VAMs hinge on our ability to sort the causally relevant from the irrelevant and the external causes of performance from internal ones. But how do we even go about knowing when we’ve sufficiently accounted for external factors and properly weighed them? How would we feel confident that the model is comprehensive enough to produce meaningful results about classroom performance that could be leaned heavily upon in tenure and promotion decisions? Again, not at all clear, at least not at this point. VAMs therefore turn out to be extra pernicious because they give the powerful but false impression that we’re talking directly and purely and with precision about how an individual teacher contributed to overall student learning. And this type of report will be used by the State of New York to formally evaluate teachers, which is, simply put, a travesty.

The NYC DOE apparently recognizes and admits*** the report's limitations by listing individual teacher scores with margins of error of 35 percentage points for math and 53 for English. Doing so, though, reveals the rankings as farce as well as travesty. Even a 35-point swing means a teacher rated dead average by the DOE’s model (a 50) could for all anyone knows be an Above Average 85 or a fireable Below Average 15. The swing is even more dramatic and therefore more risible for English scores. As commenters on various New York Times pieces quickly pointed out, metrics with this kind of error slack would be laughed right out of most anywhere else. Consider: “In 2012 Jeremy Lin had a field-goal percentage between 27 and 80%”; “Last year this fund had a rate of return of 9%, give or take 35%;” and, more pointedly, “Chancellor Dennis M. Walcott performed his duties somewhere around the Below Average or Average or Above average level,” etc., etc.

Look, I’m not one of those Teaching Is An Art Not A Science people. I’ve been working in higher education for around 15 years as an instructor and administrator. Colleges and universities have likewise been swept up in assessment mania, and I see and hear lots of resistance to attempts at evaluating what students gain by attending a particular institution. Push-back in many cases is warranted. But principled resistance — resistance to the idea of evaluating what you do in your classrooms as a teacher and/or a administrator — sells people and disciplines and institutions extremely short. A teacher of any sort should be able to say pretty explicitly what she wants students to learn skill- and content-wise, how she plans to get her students there, and how she will figure out whether they’ve made it.**** Assessing teaching and learning isn’t easy, of course, on any level, but it’s worth doing and doing well. The problem is, “well” most likely means either more individualized and extensive personal evaluations of students and their teachers (hyperlocal) or, if you like your tests standardized, more aggregate measurements of entire districts or systems looked at as aggregates à la Finland. Either way, “well” means not viewing the results as opportunities for punishment and reward. The NYC teacher data dumped last week doesn’t get close to assessing well: It’s too flawed, too personalized, too high-stakes, too susceptible to misunderstanding and misuse.

I could go on. I could speculate about why the NYC DOE and the state would distribute and base decisions this report, but that exercise always pushes me downhill into despair to the point where I begin to wonder exactly when we stopped being serious about important things. I’ll stare into these abysses on my own time.

I do, though, want to spend a little time here not understanding why the New York Times acted as it did. As the Times itself will tell you, the paper sued to obtain the teacher data and won, despite the protestations of the United Federation of Teachers. No problem there; the data being used to hire, fire, and promote public school teachers should be looked at by people other than those who hire and fire. However, the real story turned out to be the extent to which this data is flawed and misused. But the Times published the data itself anyway in an easily searchable form, thereby making it nearly effortless to gawk at the results that various of its writers wring hands over.

If the data is so bad and misleading, why publish it? Here’s the Times’s answer:
Why did SchoolBook decide to publish these evaluations?
The New York Times and WNYC, who jointly publish SchoolBook, believe that the public has the right to know how the Department of Education is evaluating our teachers. Since the value-added assessments were being used for tenure and other high-stakes decisions, we sued for access to the reports. While we share some critics’ concerns about the high margins of error and other flaws in the system, we believe it is our responsibility to provide the information, along with appropriate caveats and context, for readers to evaluate.
Sorry, but I don’t buy it. If Times writers and editors really did “share some critics' concerns” to the degree indicated by their treatment of this whole issue, they wouldn't have made it so simple to see the 36 given to your fifth-grader's teacher. The data could have been anonymized and/or excerpted for publication. As is, the concerns and caveats preclude any proper context for these results: I have no way of knowing whether the competence of my kids' teachers falls on the thick black error bar let alone where. Putting up a mechanism for teachers and the general public to respond doesn't help either; those kinds of things don't receive the same level of attention as the numbers themselves. In my more cynical moments, I begin to think that the actual context for the story involves the Times's pageview counters.

Teaching is good, hard work. I remain puzzled why we seem so determined to make being a teacher so difficult.

*Pardon the cringe-inducing quotes. **A yellow-bus sized assumption there, of course.
***I did have “pretends to recognize” and “sort of admits,” but I'm still trying to exude a generosity of spirit here.
****In many ways the problem for higher ed is more acute because college-level teaching involves somewhere around zero hours of required faculty development or teacher training, even though it's almost a theorem that research performance is inversely proportional to teaching ability. Lord knows I struggled early on in my classrooms, and I still find myself confounded sometimes. K-12 teachers at least have to go through education courses and student teach, say what you will about their training.