Constructivism posits that learning is an active process where learners construct new ideas based on previous knowledge. Key theorists include Piaget, who believed children learn actively without adult motivation; Bruner, who said learning involves constructing new ideas; Vygotsky, who emphasized social learning and culture; and Dewey, who viewed education as social. In constructivist classrooms, students are encouraged to be autonomous, use hands-on materials, and communicate their understanding with teachers and peers to actively construct knowledge. Assessments focus on the learning process rather than standardized tests.