If you have set up a safe and inviting learning environment in your classroom, students should feel free to contribute openly, without fear of "messing up".
Today we were representing numbers in different ways, using base ten blocks. A student shared all the numbers she had made using only 16 tens and ones blocks. (rods and units) As we were debriefing her solutions, another student pointed out an error in her work. She had used 16 tens rods to make a number, which she had recorded as "700" on her whiteboard. (See black boxes and red arrows in the screen shot below.)
Interestingly, the student who pointed out the error had also used 16 tens rod to make a number, and as a class we had just looked at his solution. The IWB allowed me to revist the previous solution and notice that there was a descrepency.
"Look!" I said, "Both Student A and Student B used 16 tens rods to make a number! One of them said it was 160, the other said it was 700. I guess one of them was wrong. Whose solution is correct, and how do you know? Turn and tell a partner." Then I let Student B tell what she thought (she had been the student who had made the error), and she soon realised where she went wrong, and was able to explain her thinking as she revised her work.
What a powerful opportunity for learning!