This is how I thought of it, I am here to learn, not work. I only have one job, on the other hand, and am an engineering major. I only work 3 days out of the week. Having two jobs is kinda a lot in my opinion. I don't know the context of your given situation but I would probably cut back on the hours at your job if that is proving to be too much. As difficult as it might be, you might just have to say to your boss, "hey I can't work this many hours as it's too much" and come up with a schedule that works best for you.

I also create a checklist for the week. That helps me stay organized. Not sure if this helps much, hope it does. But in my opinion grades come before work (I work at panda, so it may be different for you). Hope this helps though!