My sons's servieces are being terminated!

My 16 year old son, who has been diagnosed with Aspergers and in special education since he was in 2nd grade has just been re-evaluated and found not eligible for services. The reason that he found not eligible is because he is making good grades and scored high on are standard of learning test. All of his teachers thought that he should continue with services and that the only reason that he was doing so well was because he utilizes all of his special education services. The school psychologist recommended that he be switched to a 504 plan. I did not sign off on services and was told that because I did not sign off nothing would change, but now I and everyone else on the panel that did not agree, were instructed to write a letter explaining why we disagreed and the staff is scheduled to have a meeting that I am not invited to. He has a low processing score of 70 and an over all IQ score of 79 the rest of his scores were either below average or average. I really would like to know what our rights are and how to stop this from happening. My son relies on his resource teacher and would not be successful without services.