I just answered this question about a player feeling left out in a gaming group. It came to light after I posted that the DM is his teacher, rather than a peer.
It seems plausible to me that the DM might be intentionally favoring certain players because they're "problem kids" at school. This club could be a social outlet for them to feel like they're doing something amazing where they otherwise might be struggling in school.
I base this speculation on an almost identical situation that happened to me in grade school with an after-school gaming group. One player was socially and academically struggling in school and the teacher overseeing the group favored him to give him a positive experience within a (technically) school environment.
Obviously it's entirely speculation here since my experience isn't guaranteed to match the OPs, but mentioning this dynamic might shed some light on why the teacher is favoring certain students.
I honestly have no idea if I should include this detail in my answer. If I'm wrong about it it could possibly be seen as super insulting to the players. If I'm right, it could make the situation make more sense.
I'm leaning leave it out but would welcome thoughts.