Can My High School Do This?

I am homeschooled. I've been homeschooled since 8th grade because I have ADHD and ADD and didn't do very well in middle school. I can control it now, but that's beside the point. I do a lot of things at this school. I play baseball for them and help them win championships, I went to prom, senior ball with my ex. I pay their activity fees and my family also pays taxes which inevitably go to that school. I even attend VOC and ride their bus to go to the vocational school for 2 hours. However, there's just one issue. They will not let me walk at graduation and they won't let me do project grad (project grad is directly after graduation and they basically just hang out with you all night and take you places like bowling and you get to go up a mountain at 4AM and watch a sunrise. It's basically to stop graduation parties).

They've even prevented me from going to a specific college. How you ask? The school (Syracuse University) requires that homeschool students get their program signed off on by school administration. They refuse to do so, completely preventing me from going there. Instead, I'm going to Bryant University. My parents have been fighting with the superintendent for months about this, and he will not budge. We've offered to pay my senior dues, cap and gown, etc. and they still won't let me walk.

The problem is, I want to walk. I want to graduate with my friends; the people I've grown up with. For god's sakes it's not like we don't pay taxes or anything. We pay a LOT in taxes! What can I legally do about this? Is this all illegal in one way or another? I live in Maine. @Business Attorney I would appreciate your input