Like all Vygotskian ideas, the zone of proximal development (ZPD) is a complex theory, but it can be reduced to a few simple principles that are quite easy to understand. First, within any domain of human knowledge, there are problems that an individual can solve easily and there are others that are too complex to be solved by an individual. Between these extremes, there are problems that can be solved with assistance. According to Vygotsky, educative experiences—those that build learners’ skill—are those within the ZPD. This is familiar to all teachers: if the curriculum is “too easy” or “too hard,” students pay little attention and make little progress. When the curriculum is “just right,” students “get it.”
The challenge of ZPD for teachers in classrooms designed for Industrial Age education (with standardized curriculum, assessment, and rigid scheduling) is that the ZPD is different for different individuals (even for students who are in the same class and thus have ostensibly been exposed to the same experiences). Many factors affect the rate at which an individual’s ZPD changes and one’s ZPD can atrophy over time if the skills are not practiced (as anyone who passed high school math, but is stymied when helping their children knows).