For providers, there are several listed on this recent thread. The subject in question was ADHD, but the places recommended aren't limited to that.
http://www.dcurbanmom.com/jforum/posts/list/490357.page
Sorry about the paranoia reference, but this sentence in your post by itself suggested it:
"He is convinced it is the school's doing this to ruin him."
If, however, this was short hand for he thinks the school was trying to ruin him because they did not give any notice, then he is just engaging in hyperbole. I am a little surprised, though, that a 15 year old had not noticed slipping grades.
That said, my 12 year old once brought home her portfolio of papers, which were all As. The report card three days later was a D. The teacher agreed that was indeed the portfolio sent home and that the required notice hadn't been sent, but all the As did not reflect her true grade, and any grade assigned could never be revoked. Never got to the bottom of that one but I suspect she was misgraded and the teacher didn't want to admit it.