While protecting the safety of youngsters at work is a good intention, some labor laws go way overboard.  Limiting work to 3 hours a day on school days is ridiculous. 

I regularly worked 4-6 hours a day on school days at my grandfather's cannery with no harm done.  I appreciate it to this day as I learned a work ethic that has served me well over the years.

I also had a girlfriend in my younger days who at the end of the school day would go home and do her homework, then hop a crew bus for an hour drive to a shake mill where she worked a full 8 hour shift, packing shakes, then rode the crew bus home and caught a couple hours sleep before school. She'd also sleep on the crew bus.  You might think her grades suffered, but she was pretty much a straight A student. She is also a very successful business woman at present.  Working did not hurt her.