When I homeschooled my kids, I would teach them something, and then have them "teach it back to me." My thought was that if they could teach the material to someone else, they had a good grasp on it. This also cuts down on boring paper work, tests, etc. and can save you time while also helping to improve their communication skills. Having an older sibling teach a younger one is good review for the older, while helping you out at the same time.