I understand the efforts you are trying to make here- and they may require bigger guns than you, the students, and the mentors can bring to the table.
Why don't you consider mailing your regional director for FIRST and ask him to escalate your concerns up the chain? Being an outside force he (she) may be able to bring in legal counsel as well to help interpret the laws that the school district has made.
Don't do this alone- use the FIRST structure that is available to help you.
If you don't know who your regional director is, try emailing Bill at Bill's Blog
http://frcdirector.blogspot.com/