I did not have an issues with this when I was a student on a team so unfortunately I cannot give any first hand advice. I would recommend that you utilize some of the NEMO resources available at
http://www.firstnemo.org/resources.htm , more specifically the A Mentor Is document would be a great thing to show them.
There are also other threads out there on CD that discuss this issue in detail. With that being said I applauded you for everything you have done so far, your actions seem very mature and acceptable thus far. Perhaps contacting your schools administration is the next step.
FWIW your team number is visible on all of your posts, an unfortunate CD policy. Meaning all of your team members and mentors can see it, something you may not want to happen. If you would like to discuss your issue in more detail please feel free to PM me.