Learning is a social activity. A key concept in Socio-Cultural Theory is scaffolding - what happens when people assist each other in learning. This assistance needs to be done well. Just telling answers to groupmates is not scaffolding, because at a certain point, the scaffolding needs to be removed, and each person needs to be able to stand alone without their groupmates’ support. This is where the CL principle of individual accountability comes into play. Educators scaffold for students, but most classrooms have only one professional educator. Fortunately, students can scaffold for each other, providing a classroom-full of scaffolders. Plus, “Those who teach learn twice”; thus, the scaffolders assist not only their peers but themselves as well.

Another key concept in Socio-Cultural Theory is Zone of Proximal Development (ZPD), which refers to what students are ready to learn. Asking most 10-year-old students to count to 20 is in their Boring Zone, because the students have probably long ago learned to count to 20, rendering the task boring. On the other hand, asking most 10-year-olds to do advanced calculus would fall into their Panic Zone, because they probably lack the necessary background to do such calculus, rendering the challenge level to be too great.

The ZPD represents the appropriate level of challenge: not boring, not panic-inducing, just right. For example, elementary algebra or division of fractions may be in the ZPD of 10-year-olds. The CL principle of heterogeneous grouping helps in two ways to put tasks into students’ Challenge Zone. Higher-achieving students have the extra challenge of teaching their lower-achieving peers, and the lower-achieving students have the support of the scaffolding of their higher-achieving peers, thereby making tasks more doable.