Care should be taken to give children worksheets that they are capable of doing. This involves understanding and monitoring the child continually, since the level of attainment of different children would often be quite different. The worksheet should challenge the child but not overwhelm her. If the worksheet is too easy or too repetitive, it may bore the child and she would not be happy. If the activity is too difficult it would frustrate her and she would not like to take up more sheets. The children should love to do the worksheets; they should not be thrust upon them. Also doing only worksheets alone repeatedly would not be very productive. You should have a range of physical games and activities as well that would reinforce the concepts learnt.
Today we all know that benefits of math are considerable. Math is not a subject one learns by reading the problems and solutions. American children have very little practice with multi-step problems, and very few opportunities to think their way in to and through problems that dont look like all the others. With a packed curriculum and the increased emphasis on testing, our children are taught tons of procedures - but procedures disconnected from when to use them, and why. Sustained thinking - the key ingredient to math success - is painfully absent in too many math classes.