I love this story about the role teachers play in PBL, from teacher Elisabeth Bostwick in Horseheads, NY:

When colleagues have entered my room, at first glance they thought I wasn’t there. I recall the bewildered look of one administrator that I worked for as he scanned the room thinking I had left it unattended. Typically one of the student leaders in my room will notice and point them in my direction. You see, as a coach I’m beside my learners as I question, reflect and provide feedback.