> Time spent in sports is fun, not work.

It is fun when it is fun, when you can skip it or do it purely because you want to. If you go to sports club because you have to, it is work and not fun.

If you go volunteer or have to join the club for college application, they become work. They are not fun stuff.

> Time spent in gym class and lunch is not work

Gym class is work. Kids are not there voluntarily.