If you have read my article "Helping Your Child With Basic Arithmetic? Stay Away From Worksheets" then you know that I am not a fan of traditional worksheets. After writing that article, I found another credible teacher who has written many ezine articles expounding on the benefits of worksheets. I decided some clarification of position is in order.
The primary problem with most math worksheets is that the problems are already written out and the child need only write the answers. For learning and practicing the basic skills of addition, subtraction, multiplication, and division, it is much more beneficial for the child to write out the entire fact and say the entire fact out loud. A child will learn a multiplication fact much faster if they are writing out 6 x 8 = 48 at the same time they are saying "six times eight is forty-eight" than if they just see 6 x 8 = ___ and only have to supply the 48.
Rather than using worksheets, a better method is to use individual size white boards and have the child writing entire facts many times. Having a child writing 9 x 7 = 7 x 9 = 63 while saying "nine times seven is the same as seven times nine and is equal to sixty-three" is many times more successful than a worksheet with 9 x 7 = ___ and the student just thinks the answer once and then writes that answer on the duplicate problems.
I will admit that there is one type of worksheet that I used in the past and found relatively beneficial, although it had a different kind of flaw. For my Basic Math, Pre-Algebra, and Algebra classes, I had several books of "self-checking" worksheets. These worksheets had puns or puzzle questions at the top, and as the students worked the problems they were given some kind of code for choosing a letter to match that answer. If they worked the problems correctly, the letters eventually answered the pun or riddle. Students enjoyed these worksheets, but there are a couple problem areas even with these worksheets. Some students would get the answer to the riddle early and then work backward from letter to problem answer, so they weren't learning or practicing anything.
Another problem with almost all worksheets is that they don't prevent incorrect answers. Self-checking worksheets just let the student know they did something wrong--after the fact. I am a firm believer in the concept that, if at all possible, learning should be structured in small chunks in such a way that there is very little possibility for error. Worksheets often allow for mistakes to be made and then to be repeated many times. A mistake that gets practiced is extremely difficult to correct. This especially happens when worksheets are used as time fillers or baby sitters and the work isn't really being supervised.
There are some new materials being developed now based on what we are learning about how the brain learns. These brain-friendly materials should be an improvement over what has existed. I recently bought a book by Marcia L. Tate titled "Mathematics Worksheets Don't Grow Dendrites." I highly recommend her book. She gives a great deal of information on alternative activities that are better for your child's brain development and for learning.
No matter what materials you choose, it is most important that you supervise your child constantly so that mistakes get caught rather than practiced. I learned this particular lesson the hard way. When my daughter was young, she did something that needed "attention." I no longer remember what it was that she did, but I told her to write the sentence "I will not disobey my parents again" 50 times. I should have known better, but I didn't check on her at the beginning and then I got busy. So, sometime later, she brought me 50 sentences of "I will not disobey my parents agen." She had just practiced misspelling "again" as "agen" -- 50 times! I'm not certain that we ever really got that fixed.
This issue of NOT practicing mistakes is extremely important. Parents shouldn't give worksheets as busy work and teachers should only use them if you are going to have a non-math teacher substitute. White boards with supervision are always a better way to practice skills. If you need some time to do chores, your child will get much more benefit by helping you with the chores. And maybe you can work in a little discussion of numbers or counting while you do chores together.