Jill Minnich. This is a site designed for K-12th grade students that allows students to improve their math skills through a variety of online games/competitions. Best of all, there is an educational portal which allows a teacher to sign up their school and track their students. Also, this site is free and aligned to state standards; plus it has the ability to adapt to students needs to get easier or harder depending on how they do.
I highly recommend checking out Magna High by clicking here!!!
For another excellent site for learning math through educational games check out, DimensionU.