More important than learning science, students need to learn to work in a community, thereby taking on social responsibilities. The most significant contributions of PBL have been in schools languishing in poverty stricken areas; when students take responsibility, or ownership, for their learning, their self-esteem soars. In standardized tests, languishing schools have been able to raise their testing grades a full level by implementing PBL.
PBL is significant to the study of (mis-)conceptions; local concepts and childhood intuitions are hard to replace with accepted science through didactic and transmissional epistemologies. In PBL, however, project science is the community culture; the student groups themselves resolve their understandings of phenomena with their own knowledge building.
A related pedagogic approach, problem-based learning is similar; however, problem-based approaches structure students' activities more by asking them to solve specific (open-ended) problems rather than relying on students to come up with their own problems in the course of completing a project.