I just looked at the link for IXL math. I had never heard of it. Might be something I consider for over the summer. My kids already get a math book they have to do over summer and return to school when they go back, so this will be a great addition. Does it allow a child to move along above level too?

As another source, my DD loved the Flashkids Gifted workbooks. They have a lot of logic problems and analytical thinking vs. just basic math problems. The reading and english were good too. I got the books at B@rnes and N0ble. We got them two years in a row. I found the basic summer bridge books much too easy, but these, since they were intended for gifted, were a little harder (not hard, but fun and colorful, and somewhat higher than the grade level books).