Solid athletic swing... would advise spending time to hunt down a reputable and accessible hitting coach that can refine his swing where needed. Make sure the hitting coach incorporates "approach at the plate" while he tweaks the swing. High school ball almost here, you don't want to be doing serious mechanical changes, just some tweaking...he has to be ready to perform soon and not caught up on mechanics.
Similar to what IronHorse said, avoid the message board coaching. You'll likely get too many inputs which could work against your son's development. A lot of these will be high quality, but just too many.
What area do you live in? You'll likely get a few good referrals from this board.
Cheers...
(edited a typo..)