Thank you both so much, @bridgenail and @indeestudios , for the helpful and specific information! I tend to be the kind of person who “plays it by ear” (so to speak, as I have no musical ability whatsoever 
), but it just started occurring to me that my son really should have some idea of what to expect when he gets to wherever he ends up. I don’t want his happiness at being able to attend a jazz program to be spoiled by the feeling that he’s out of his league–at least in terms of knowing the ropes a bit–so I thought I’d better ask.
But you’re both right–it should work out just fine. If he made it through high school he can make it through anything, especially in a placed where he’s appreciated for doing what he loves.