DS - outlier - has a verity of friends. he has one close friend,equally outlierish. But he then has a series of overlapping 'functional' friends - music friends in school / music friends out of school / football friends / chess friends. In the latter, academic ability is unimportant - it is the shared passion that counts.
DD has a group of close friends in school. They are all well-behaved, non-silly girls who love netball, and come from across the academic spectrum. She then has dance friends, who dance with her 10+ hours every week.
If you have an academic outlier - and believe you me, DS has been a total outlier, leading to selective mutism, stress and total social isolation - then actually one of the very best things you can do, IME, is find them an interest that they are passionate about - music, dance, chess, Scouting, whtaever. That is where my children have found their friends, because the shared interest gives a 'structure' in which my quirky kids have found it easier to make the appropriate social moves.