Actually, losing their accreditation might be enough to convince a court that you shouldn't be held to the 90 day notice requirement. I'm not a lawyer, but it's entirely possible your lawyer could get you out of all or part of that 90 days.
For that matter, the "settlement value" of them suing you for 90 days tuition is likely (see your lawyer) to be less than the full 90 days tuition.
After getting my child, I wouldn't pay a red cent (even of back tuition if you're behind in payments) until I'd consulted an attorney, laid out the entire situation, and found out if I really had to pay and how much.
You can either get a referral from your local bar association to an attorney, or here is a site for special education attorneys--I have no affiliation with any of these people.
http://www.edlaw.net/I don't know if a special ed attorney is what you need, *but* they may have some of the specialized knowledge of knowing the ins and outs of facilities. Or talk to your local bar association and tell them it's a dispute with a facility about the bill and their services and whether they misrepresented them. Maybe they can give you a good referral to an attorney who can handle that kind of thing as a general consumer business dispute.
Timoclea
What a distressing contrast there is between the radiant intelligence of the child and the feeble mentality of the average adult.
-- Sigmund Freud