There are other sources for worksheets also. You can find many public schools and private schools which will provide free worksheets for you if you buy textbooks from the school.
So what kinds of worksheets should you get? Anything where you feel that your child needs further drill. We often have this notion that worksheets are just for math. This, of course, is not true. While they are excellent tools for reviewing math facts such as the multiplication tables and division facts, they are just as useful for reviewing parts of speech or the states in the union.
In other words, they never memorized their multiplication tables! Many times I have seen a student do poorly due to a weakness in basic math facts they should have learned in third grade.
It is amazing the difference in effort you will get from worksheet to worksheet. Granted the amount of effort may vary immensely from year to year depending on the group of students you have.