Save Money : It's easy to see how free worksheets can save you money. If you want, you can skip buying math books and just use worksheets that you get for free on the internet. All you need to do is use a "scope and sequence" book that tells you what your child needs to be doing in math by age and grade. This book is essential when you homeschool.
Or you can usually find textbooks and workbooks at the public library, where you can also copy any worksheets that you want to use.
However, caution must be taken into account when review is repeatedly covered in your classroom. You do not want your students to become bored or frustrated with the repetition.
From a teacher's perspective our competition is tough. Passing out a handout of 30 problems that are all in a format of 534x25= is not as stimulating in the students' eyes as playing games such as Grand Theft Auto and Resident Evil.