It is difficult for students to learn to consider, evaluate, and build on
the thinking of others, especially when their peers are still developing
their own mathematical understandings. A good setting in which young
students can share and analyze one another’s strategies is in solving
arithmetic problems, where students’ invented strategies can become
objects of discussion and critique. Students must also learn to question
and probe one another’s thinking in order to clarify underdeveloped
ideas. Moreover, since not all methods have equal merit, students must
learn to examine the methods and ideas of others in order to determine
their strengths and limitations. By carefully listening to, and thinking
about, the claims made by others, students learn to become critical
thinkers about mathematics.