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.
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 don't 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.