So what is the concern? There are three big concerns, actually. Our teacher "caution light" should start blinking if we are using lower_level_thinking worksheets (Example: "Check the box next to the correct answer."), if we are using too many worksheets or if we are using worksheets as classroom busy work.
As far as using worksheets for busy work, the verdict is in. It is destructive to classroom learning to assign worksheets to simply keep students occupied. Busy work creates monotony, causes boredom and increases the likelihood of behavior problems. To know if you are on the right track with worksheets in your classroom, answer (honestly) these simple questions: Do my students groan when I hand out a worksheet? (The answer should be no.) Are my lesson plans based on worksheets? (The answer should be no.) Do I feel anxiety if I don't have worksheets copied? (The answer should be no.) Are students excited about learning in my classroom? (The answer should be yes!).