This has to be one of the hardest things to do in school, and it's a challenge I did not personally face because I was too chicken to take it on. Now, having been unemployed for so long, I wish I had started getting work experience while I was in school. I would have learned the following tips from my life instead of reading about how others did it!
Complete homework on class days when possible, so that it's not hanging over your head at work.
Take power naps (20 minutes) to recharge.
Use any downtime to complete schoolwork way ahead of time.
Take online classes, so that you're not having to spend money or time traveling to and from class.
Do not over-schedule yourself.
Make sure your boss knows you're still in school.
When possible, use your gained knowledge from school at work.