My pre-schooler (he is 3) is in a special needs preschool which focus on ASD, ADHD and a few other things along that line. He currently does not have a diagnosis (he didn't get one from the neurologist though he says he has some autistic traits). We have not shared this lack of diagnosis with the school district since we do not have to and it could only hurt us now.
We had him evaluated by the school district. He was evaluated by the ST, OT, PT, psychologist and social worker. He has significant communication delays and a short attention span (unless he is interested) so it was fairly easy to get services.
The school district pays for ST, OT, PT, psychologist/play therapy. The also pay for the 22 hours of "school time" for him. He see each of his therapist 2x a week for 8 visits a week. He is pulled out from class to meet with his therapists. In total, his services are approximately $45,000 a year. We had to be evaluated by a school in our school district but we could choose to go to any school in NYC, as long as there was space and the distance was "reasonable".