I dont' think you would get evealuated by CPS just by having him in the school unless someone reports you or something about your child, etc (bruises,etc). Was he held back, you metion he's in Pre-K and he's seven. Was he speech delayed? My son is speech delays and sometimes we've had trouble getting him to use his words.
No one can force you to have him evaluated. You might start by going to see a therapist to see if they have any suggestions. It might help you too to talk about it.
Some of it is being a boy. Sometimes I think boys get judged harder and school is harder for them in the younger years just b/c they are less mature, more rambuctious, etc.
I don't understand, exactly -- is the school saying they want your son to be evaluated by a therapist, or do you just think it might come to that? What would be the problem with his being evaluated? (It's an evaluation, not a railroad -- in other words, they might tell you they think he has ADHD or they might tell you he doesn't.) Even if he was evaluated, it might be helpful or relieve your worries. Unless there is more to the story, I'd let him go back to public school. Home schooling is fine, but it is hard for home-schooled kids to get that social interaction with a lot of kids at once, which is part of what they learn in school.