K.B.
My mom (who is a teacher) always had workbooks for us to do. She had us do about five pages a week, sometimes less or more depending on how big the work book was. This seemed to be enough to keep things that we have learned fresh as well as maybe getting a head start on the coming school year. For me that was a big plus because I struggled in school.
My daughter loves the workbooks and you can get one in just about any subject for any age. I have gotten them at learning shops (where the teacher's shop) and Sam's Club.