>>4258457 (pb)
Required reading for home-school kids:
Animal Farm
1984
A Brave New World
Also good:
The Great Gatsby
And don't forget:
Behold a Pale Horse
I supplement good literature with vocabulary lessons. SAT lists are good. Make sure they know how to use the words in sentences, not just the definitions.
As for math and science - use your judgment to figure out how far beyond the basics you need to go. (Basics are Algebra, Geometry, Biology, Chemistry, Physics).