I just signed up my kids for this FREE!!!! Online Summer Math Learning Program called TenMarks. It is supposed to be for grades 1 through Algebra 2 & HS Geometry. You set up your own incentive program for kids to earn rewards. If you decide to do this with your child(ren), they first have to complete an assessment (it was 20 questions for 1st grade and 30 questions for 3rd grade) that does not count towards their assignments that they earn rewards from. You decide on the rewards that you want to give and the frequency. From what I can tell there is 10 questions per assignment, at least so far.
PREVENT SUMMER SLIDE!!