Constructivism is a learning theory based on the idea that students actively construct their own understanding through experiences and reflecting on those experiences. Key contributors to constructivism include Jerome Bruner, Jean Piaget, Lev Vygotsky, and John Dewey. In a constructivist classroom, the teacher facilitates learning by engaging students in hands-on activities, group work, and inquiry-based lessons that allow students to build on prior knowledge and develop new understandings.