Given your situation, I would test. You'll have more information to use in advocating for him and it won't just be a "gut instinct" or observation. Unfortunately, we waited until my son was practically depressed before we tested and once we had the results, we finally understood the extent of his outlier status. When we shared it with the school, they were totally on board with finding solutions to challenging him. The approval for a skip came within 2 weeks (they did the IAS the next week). We didn't end up skipping and we're trying to figure out additional accommodations this year, but everyone is working toward extreme accommodations-- all because of the testing. So if you need "ammo," so to speak, data is what you need. We had both the WISC and an Explore test.
