This may not be quite what your DS is trying to convey, but it reminds me of a frequent comment by my own. Maybe yours DS can find something in this that helps frame his input as more about "unusual needs of kid rather" than "avoiding bad teacher"?
My DS has two teacher requests: "cheerful", and "eccentric, like me". More practically, the latter means teachers who really enjoy coming at topics and problem from unusual directions - and really like *students* who take their class discussion in unexpected directions. Such teachers think it's neat when students propose approaches, problem-solving strategies and ideas they've never heard of before, and feel challenged and excited to try out this new concept, rather than derailed from their lesson plan.
Other somewhat more neutral descriptors of possible use include: flexible, out-of-the-box, not linear, non-traditional.... a little googling and thesaurus might give him some new wording ideas. Good luck to him - I think it's awesome he's prepared to go in there at 9 and try to explain his needs and concerns.
