To a degree, you can advocate for your program and for more prep time. Or you can do less - simplify what you're doing in class so it doesn't take as much work. It's hard to have a good program when your school doesn't give you enough time to do the work required. I know my former school didn't care much about the arts, they just needed a place for kids to go when they weren't in math or english class.
My eventual solution was to leave and find a better job. I know that doesn't help you for this year, but looking ahead to next year...