I have a 10 y/o son in 5th grade. I checked out the contained classrooms, and what I saw was not for Zach. He is educationally about kindergarten/1st grade level, but has a high vocabulary. The kids in the contained classrooms were more affected by their disabilities than Zach in many ways. Between his Abilify and being around his age group, he has progressed so much in the last year, and I thank his school for mainstreaming him and keeping him in a resource room environment several hours each day. He has a schedule like lunacopia's daughter had, and it works very well for him. I think being in a contained classroom would have frustrated him and held him back. He was even in band this year, performed on stage, and was very proud of himself! Two years ago, there was no way he would be in front of people performing.
After 6th grade, I'm not sure what will happen, as I don't think he'll be able to handle the junior high/high school environment. We've been really lucky with how wonderful his classmates are with him. I love that when I drop him off to school, they say hi to him and walk with him into school. Upper grades are going to be a lot tougher, so I am exploring what options we'll have for 7th grade and after.
JSB, stick to your guns and go with your gut. You are you child's best advocate. There is such a difference from one school district to the other as far as what resources they have to offer, based on their budget. Check into school of choice, if your area has it. That's what I did, and Zach goes to a school out of the district where we live.
Good luck to you and your son.