Form a club or organization. High schools often encourage students to form clubs with the support of a sponsor (usually a teacher or parent).
Don't forget the public library!
If your school doesn't already have a College Preparations club (and won't let
you start one), then get a group of like-minded students together and meet regularly at a public library. Many libraries have private rooms that can be reserved for free (or a minimal charge).
Groups can make studying more fun, and it's easier to be consistent with a regular study program when you have a buddy system.