Are future creative geniuses unpopular in high school?

Yes. The deliberate practice that will one day make them famous alienates them from their peers in adolescence.

Via Quiet: The Power of Introverts in a World That Can’t Stop Talking:

…the single-minded focus on what would turn out to be a lifelong passion, is typical for highly creative people. According to the psychologist Mihaly Csikszentmihalyi, who between 1990 and 1995 studied the lives of ninety-one exceptionally creative people in the arts, sciences, business, and government, many of his subjects were on the social margins during adolescence, partly because “intense curiosity or focused interest seems odd to their peers.” Teens who are too gregarious to spend time alone often fail to cultivate their talents “because practicing music or studying math requires a solitude they dread.”