The school’s going to change as time goes on, but it was founded “for kids who love math…” not “for kids who are gifted at math.” That said, there are definitely some off-the-charts kids there whose parents literally didn’t know what else to do with them–kids who were homeschooling studying math multiple years ahead of their public school peers, kids who were taking math classes at Berkeley, and kids who breathe and live math. But there are some well-rounded regular kids there too, and the current aim is to meet the needs of all of them. And by the time someone’s been there for a couple years, they’re going to look like they’re gifted in math simply because they spend so much time doing it.
I don’t think it would be a good match for a kid who picks up math concepts really slowly, can’t handle Algebra in their first year there (if you go in 6th grade, you’ll take Algebra I), or thinks it would be torture to have to do math for 2.5 hours a day. If a kid likes puzzles or board gaming, they should be fine–anything that shows that they like to think through possibilities and solutions.
All that said, the school is not looking for tiger parents. Maybe things will change, but right now, they try to keep a low-stress, fun environment and they want kids who generally want to be there, not parents who are pushing their kids to be there because they think it’s the path to getting into Caltech or MIT.