I love Summer Bridge Books!
I think they are the best thing ever for students during the summer months. I know this year has been crazy but I do believe these books are likely to still be helpful and fun as well! My kids when they were younger enjoyed them and it really was awesome when they went back to school each year and were doing just fine and reduced "summer slide." I know many will have more than that but it is worth the try.
There is a book that begins with PreK - K all the way through 7-8 ! This is awesome!!!