The zone of proximal development (ZPD) refers to the difference between what a child can accomplish when working on a task alone versus with the assistance of a more knowledgeable person. This zone includes all the skills the child is on the cusp of learning. Children are in a constant cycle of learning from more knowledgeable others. Social interaction acts to stimulate cognitive growth in these situations. Social partners use cultural tools, like language, to help close the gap between their own knowledge and the child’s knowledge. Over time, the child’s zone moves upward, allowing them to perform more tasks independently and engage with higher-level thinking. When designing lessons, teachers should aim to be within the ZPDs of their students in order to encourage cognitive growth. ZPDs vary amongst students, and thus teachers should also offer individual guidance in addition to cooperative learning opportunities in the classroom.