Ask HN: Online Math Community for Kids?

My son is 9 years old, and really enjoys math. He recently expressed that he doesn't feel like he fits in because already in school it's not cool to like math. He's doing fine socially, it's primarily an academic frustration. Are there any good online communities focusing on math, for kids to participate in? I'm a former math teacher, so I'm not looking for activities, I'm looking for ways to give him interaction with other kids around math. We live in a remote area, so I'm looking for online communities.