I interpreted it slightly differently...that Adam and Kristina wanted Max to be "well-adjusted" so badly (and so desperately) that they prematurely put him back into regular school without fully thinking it all the way through. And the writers dropped the ball even further when Max's parents never realized or admitted what an awful decision they'd made.

If you haven't gotten to Season 6 yet: Max's school situation changes, at that point, in a rather intriguing (but still sort of clumsy) plot development.