A major idea in constructivism is Vygotsky's Zone of Proximal Development (ZPD). The ZPD is the gap between what a learner can accomplish unaided, versus how much they could achieve with help or collaboration. For example, a child may not be able to put together a puzzle themselves, but after a teacher hints or after seeing a colleague demonstrate the puzzle, they may successfully put the puzzle together.

This is a powerful idea because it emphasizes that learning is not solely an individual activity. It also emphasizes the social and interactive nature of learning. The ZPD centers on the important social aspect of actions in scaffolding by being ideal for teachers or peers providing learners temporary support until they are better able to manage on their own. It also encourages teachers to understand that a learner's mistake is not viewed as failure but as being within a learner's ZPD and an opportunity for a constructive educational experience.

Nevertheless, the concept has criticisms. Some researchers argue that measuring a learner's ZPD is almost impossible; therefore they argue teacher's can't consistently apply it in classroom settings. Furthermore, sometimes constructivist approaches to learning de-emphasize the role of instruction (direct teaching). Thus they miss opportunities to teach more quickly and efficiently to learn some types of knowledge and skills (e.g. basic math facts).