My house is currently home to myself and three kids. It's 1400 sq. feet. I make it work, because I don't have a choice.
I also kind of come from the school of thought where I refuse to be a slave to my house, both financially and cleaning-wise. I wouldn't want a HUGe house, but yeah, I'd love to move to a better district and more space. Even a little better and little more. I say weigh the pros and cons and really think it over to make sure it's in your price range. School isn't everything, as kids will eventually not be in it.
Have you ever looked into state programs where a one on one aide can work with your son both during school and after, at home? There are state programs that provide this, though I'm not sure where you live. Just a thought for you. GL!