ZooWhiz is a good — and free — Australian site with tons of interactive games and exercises for pre-school, elementary, and middle school (and for English Language Learners who are even older).

Users have to register for the site, and teachers can create virtual classrooms for their students.

I’m adding it to:

The Best Sites That Students Can Use Independently And Let Teachers Check On Progress

The Best MATH Sites That Students Can Use Independently And Let Teachers Check On Progress