Depending on the facts of your case, you may have legal recourse. You'll want to meet with an attorney in your area who deals with special education / school law issues to review the details and discuss possible next steps (which could range from a formal demand that your son's IEP be reviewed and then properly implemented all the way to a lawsuit). Alternatively, look for a special education advocacy group in your area - they might be able to help or counsel you, as well. Good luck with the situation.
You need to seek help from a special education attorney who reoresents parents. Disciplining a student with a disability is always a "red flag" that the District is not addressing the students' needs and/or giving appropriate services.. Failure to follow and/or give appropriate services can lead to the District having to provide compensatory educationa services, provide prospective services (if they can't do it, then sometimes the District is Ordered to place the sutdent in a private school at their expense), and/or monetary damages.
Your first course of action should be to ask them in writing (with proof of when they received your request) for your son to be "re-evaluated by the District for any/all suspected disabilities" if that has not already been done within one year prior to your request date. It would be better to have him evaluated by an outside evaluator if you can afford to do so or you have insurance which will pay for it. Often times an attorney can get you reimbursed for your out-of-pocket expense.
Furthermore, if you win in an administrative or other court hearing, you can get all or some of your attorney fees and costs paid by the District. I recommend the council of Parent Attorneys and Advocates (COPAA) to find a non-attorney advocate or an attorney to help you.
I agree with my colleagues. An attorney who practices school law should review your details and be able to represent you successfully. Although an attorney can't guarantee an outcome, the facts you present here seem to be in your child's favor.
973-984-0800. Please be advised my answers to questions does not constitute legal advise and you should not rely on it, due to the fact that we have never met, I have not been aprised of the facts in you case nor have I reviewed any documents.