Fellow IMSA alum here, also underage (skipped 3 grades). I'll cosign most of what atdrummond says here, but shift emphasis: to me and the majority of my friend

Fellow IMSA alum here, also underage (skipped 3 grades). I'll cosign most of what atdrummond says here, but shift emphasis: to me and the majority of my friends (many of whom I'm still in regular contact with 30 years later), it was specifically being around other kids like us that was a godsend. The diversity was also broader than at most of our previous schools. The academics were an important part of it (not least to justify the state funding) but the unique value for a lot of us came from the nonacademic parts. Re the OP, I wonder what's next for him. I know that college was a little weird but manageable as a freshman at 15; a junior at 12 is going to have an even more different experience (and then... grad school at 14?) But if he's motivated and it's not just his parents driving this, he'll come up with something and do fine, I'm sure.