It doesn't sound like he's a good candidate for fourth grade math next year, unless he does a lot of work over the summer. Then again, it doesn't make sense to cram over the summer to make a stretch.
I think it could make sense to after- or homeschool him for math, perhaps starting with third grade curriculum compacting (i.e. pretesting and letting him skip sections where he demonstrates already-achieved mastery). If you do this, I'd ask permission to send written work to school for him to do during math period, so his time isn't wasted. DS7 has shown the ability to happily learn math many times faster than normal this way, with approximately a half hour of home instruction per week, the rest self-paced work during math period at school.
Does he show above-average aptitude in other areas?
