A kid's science site from Lawrence Hall of Science at UC Berkley. There several interactive activities, online games, and hands-on experiments available for free. You can also purchase classroom science kits that could be useful for co-op classes.
Saturday Grab Bag
Printable curriculum materials for preschool through second grade levels.
Thursday History/Social Studies
This website from the Government Publishing Office has resources for learning about the US govern
The name of this site says it all!
Tuesday Language Arts
This company provides programs for beginning reading and math learning.
This company publishes three books for helping elementary learners explore science.
Self-paced, online courses for learning coding.