Click on "Find help in your state" at this website:
http://www.napas.org/I'm a teacher (and former PG kid) who used to have a job where I coordinated evaluation and eligibility for disabilities (Special Ed, 504). My experience of Disability Rights Advocates is that they want what's best for the child (but don't always agree with the school about what that looks like). With your consent, they can review the file and attend meetings with you (sometimes by teleconference in our islands). They are particularly skilled at translating edubabble into language the parents can understand.
I've also been involved with Civil Rights complaints and Due Process hearings. In my experience, having an advocate is more effective than either of those routes.