Designate certain areas as school space. You will need a bookcase, a file cabinet with hanging files and folders, desk space for seat work, and a larger project area (save all shoeboxes!).
Separate work areas from play areas. Toddlers playing school under the table where you're actually trying to hold school with older children is just too distracting.
Store all school supplies in their own cabinet or other space. Make a rule that they are to be used only for school projects, or you'll find yourself five pipe cleaners short of a dinosaur some afternoon.
Take advantage of other people's space. Think library for research projects, the park for painting, or grandma's house if she has the piano.
Set limits. Not everything and everywhere has to be educational. Give your kids a break and don't post the table of elements chart in the bathroom.