I'd add that sometimes because there is no obvious next step or specfic level of proficiency required for verbal kids, I think it can be harder for schools/teachers to get just how far ahead of the curriculum they are. Math curriculum is set up as much more "first this, then that"--which is not necessarily a good thing, mind you--but it leads to a much clearer trail of breadcrumbs through the curriculum. Mastery can be easier to demonstrate as a result.

Kriston