If your child looked up five new dictionary words every night before going to bed, their REM sleep (Rapid Eye Movement) would help them remember the words and their meanings while they slept. That's an excellent start towards English assignments when they are back in school.
If your child went clothes shopping with you and while you shopped, they figured out the amount owed after the sales deduction, they would be ready for math. Everything in Math centers around percentages, which are decimals, division, multiplication, addition, and subtraction problems all rolled up in one. First they have to know that 10% simply moves the decimal point to the left one time. An example would be if an item were on sale for $ 10.00, and the sale was 10% off, then the sale would equal $ 1.000 or $1.00 off the price (hint: drop the third zero after moving the decimal to the left one time). If the sale was 25% off, then the $1.00 would be multiplied by 2.5 or two ten percents and one/half percent. The 2 would represent the dollar amount and the .5 or .50 would represent the one-half dollar amount, which would make the item only $ 7.50.
Have your child start a journal of their day to day activities during the summer months. They will learn to become better writers, think outside the box, and they will learn excellent language skills.