As millions flirt with free college-level courses online, educators are still debating their academic merits.

Elite schools allow their professors to offer courses on Coursera, Udacity and edX, but so far, most aren't willing to award students credit for those classes, which suggest that they're not fully endorsing the pedagogy quite yet.

While the most sophisticated MOOCs—massive open online courses—go beyond a video lecture, some academics still question the quality of additional content such as quizzes and group discussions.

MOOC homework assignments are often different from those required in their classroom counterparts. For example, exams may require less analytical thinking—and some users say their online classmates lack the knowledge to contribute meaningfully to conversations. Using a peer-review model to grade essays, as Coursera has done, exposes similar issues.

And only a fraction of students—under 10% in most classes—makes it all the way through those massive online courses. That's proof, some say, that MOOCs aren't acceptable replacements for traditional classes.

"There's a huge disconnect between the massive enthusiasm...and evidence of serious students who actually complete these courses," said Carol Geary Schneider, president of the Association of American Colleges and Universities.

For their part, MOOC providers say that many students pick and choose lessons that interest them, and never have the intention of working all the way through the multiweek courses. However, they say they are trying to improve retention rates. That's important not just for their reputations but also for their proposed revenue plans, as many are banking on selling certificates of completion or earning money by matching successful students with employers.

Ms. Schneider—who took a Princeton University world history class through Coursera—said the most likely path for MOOCs is probably to establish them as general education classes at community colleges and other broad-access universities. But that is also the most dangerous, in her opinion because that would target a population best helped by small, personalized classes. "If you go down that path, it will be in complete defiance of everything we know about helping vulnerable students persist and succeed in college," she said.

In November, edX announced a partnership with the Gates Foundation linking students at Massachusetts-based Bunker Hill and MassBay community colleges with courses taught by faculty from nearby Harvard University and Massachusetts Institute of Technology.

Students at those community colleges will be able to earn credit by enrolling in certain classes that are taught via MOOCs, and supplemented with classroom instruction.

Administrators at some big schools are warming to MOOCs as a way to complement traditional instruction. One experiment underway at San Jose State University could help prove MOOCs' value in augmenting classroom lessons, said Ping Hsu, interim dean at the university's College of Engineering.

This fall, students in its Circuits course—which 40% of students usually have to retake—were assigned lectures from edX's course on the same topic, taught by an MIT professor. In-person meetings were spent doing lab projects, a switch that educators call "flipping the classroom."

On the first big test, the 84 San Jose State students beat last year's average score. The class averaged a correct-answer rate of 70% on a midterm this fall well above the typical 50% score from years past.

Write to Melissa Korn at and Jennifer Levitz at