Setting up your team to be 501(c)3 is the best idea. We have that set up, along with our own account. Everything related with donations and expenses is managed within our team and the school can't touch our money.

Regarding the supervision issue, our school also requires that we have certified technology teachers with safety training, making it even harder as we cannot interest any teacher in supervising us. This is understandable because the district doesn't want kids working in a room with lots of power tools and machinery like the lathe, drill press, mill and welder.

We have solved the problem by interesting all the tech teachers we can find in "running shifts" to supervise us. If you need supervision, I would suggest bringing some interested people to an offseason and show them how exciting it can be. Or show them some videos or pictures of last years build season and competition.

If you need a video to show your interested people, I can produce a short "promotional" video for your team if you need it.