Tiago,
I'd recommend to check i.e. CWSP study guide and decide for the best authentication method for your school.
Personally, I'd rely on PEAP-MSCHAPv2 with certificate validation as I believe you use ActiveDirectory and the school definitely has a public website covered with a wildcard certificate. You could merge it then.
However, if you are not familiar with PKI or (wireless) network design, I appreciate your decision of contacting Extreme Partners.
See this article:
How can I search for a partner in my area?
Regards,
Ondrej