We've, honestly, never been totally happy with "during classtime" work (i.e. - when the intervention to meet our kids' needs has been differentiated work in the regular classroom or a parent volunteer, who was often me, pulling some kids out to work on enrichment units, it just didn't work as well). I'd give a try with requesting subject acceleration if your ds isn't in favor of a grade skip or if it doesn't appropriate.
In order for subject acceleration to work, however, the next grade up needs to run its language arts, reading, math, or whatever subject you want acceleration in during the same time that his current class runs it. That has worked quite well for both of my kids when we've had that option.
