I think a 100% student-run team is as good as a school taught by your peers. Mentors are there because they know all of the things you don't.

On the school subject, imagine a team like a school; The team members students, and mentors teachers. If the mentor/teacher solves all the problems, then the students don't learn anything. If the mentor/teacher doesn't help their students at all, then the students don't learn anything. The best results come from equal mentor : student cooperation.

Just my .02 FIRST dollars