Have you guys tried the BBC websites for math and English?

http://www.bbc.co.uk/schools/ks1bitesize/literacy/

The website goes on to KS2 and KS3.

We did not stumble upon this when my son was younger, but he did the KS2 and KS3 levels (It's stated for up to 12 or 13 yo. Very objectively, they're not at level, ie, they're great for younger kids). One particular game that my son just loved was Questionaut with the lovely graphics and beautiful music.

Enjoy!