Hello, I'm sorry to hear that your grandson is struggling. It's wonderful that you are involved in helping him!
This month (August 2010) in SchoolFinder, you can locate local Kumon Learning Centers near your grandson's school. I've included a link below to SchoolFinder. Search for his school page, and you'll see a listing of learning centers in the lower right column on the page (scroll down to see it).
There are also some math and reading help info centers available on Education.com. I'm including those links below too.
I hope these resources are helpful to your family. Thanks for asking!