The contests are aimed at primary and early secondary students, if a teacher feels this is an appropriate level for other students they are also welcome to join in.
It will only take an hour so to get a decent score, and as students play online, they can compete in school or at home.
In order to join in the fun, teachers can enter their class here:
http://www.sumdog.com/enter_contest
For questions, contact info@sumdog.com