If it's part of his IEP, they should have a specific listing of goals and reports on progress.
DS was in social skills groups for two or three years, as part of his IEP, and there were (at least dubiously) measurable goals for him -- "DS will identify and use the correct tone of voice (scale of 1 to 5, whisper to emergency voice) in 3 out of 5 instances" or something like that. They had the voice levels, taking turns talking, responding to questions properly, etc. We got reports on his progress at each IEP meeting. When they felt he didn't need it anymore, they removed the group from his IEP.
Oh, and yes, they probably get money for it somewhere along the line.
