Go back to the board of education and follow up with additional complaints about anything else that has happened since your last filing, continue to document all instances of improper conduct, and speak with an experienced attorney.
I sue the BOE pretty regularly for employees but not students. However, in my research on issues I have seen cases where parents have sued over civil rights violations committed against their children. There are time limits for suits so if what happened hasn't been resolved, or resolved to your satisfaction, it may be worth consulting with a civil rights attorney.
My answering this question does not form an attorney-client relationship. Always retain a qualified attorney before taking any action. My office offers free consultations. www.jrandolphlaw.com