Isn`t it a bit late to be planning that now, most of the school books will have been sold by now.
If you didn`t know you have to purchase the books and materials used in Spanish schools, the school will provide a list during the summer, its around 110.00 Euros per child per year, you order at any local stationary shop near the school and collect throughout the summer as they arrive.
Research on the net is a waste, when you arrive get the contacts locally to your home, then enrol them.
It`ll give you chance to view the school and decide if it right.