There are cheap soft-cover math workbooks for just about every grade level, which are good to keep a kid busy over the summer and not forget everything they lea

There are cheap soft-cover math workbooks for just about every grade level, which are good to keep a kid busy over the summer and not forget everything they learned in that grade. We have one here ... "Spectrum Geometry, Grade 5," "Pre-Algebra, Grade 8." If you want something more hi-tech there is Khan Academy of course.