Both lower_level_thinking worksheets and too many (even high quality) worksheets can hold students back by not providing stimulus and challenge. Studies have shown for years (just do a Google search!) that children learn best through active involvement and real_life experiences. Virtually every teacher knows that children learn to read by being exposed to books and by being read to, NOT by completing worksheets. The same applies to all areas of learning.
Then along came digital copiers and the purple_ink mimeograph machine disappeared. But the teaching tool that the mimeograph machine spawned _ the worksheet _ has lived on... and on... and on. For decades _ literally decades _ teachers have been enamored with worksheets. So what is the bottom line? Are worksheets a serious teaching tool or an over_used form of busy work? The answer, of course, is both.