In learning, there may be no greater tool for students than hands-on experience. Consider a classroom of first-graders who were lead in an endeavor to raise trout eggs while understanding environmental impacts. Or a high-school biology teacher who had her students create a project on any system in the human body, with results that included everything from a board game based on the nervous system to a physical model of the knee. In both situations, the teacher acted as a facilitator, guiding students as they crafted their own work, all leading to a final presentation.
More evidence of PBL that works.