How do you turn a 100 year-old blue jeans factory into a Quaker elementary school? With a light, careful touch, it seems. Join Peter Pfau of Pfau Long Architects on a tour of San Francisco's recently renovated Friends School, complete with four thermal towers, (which naturally circulates air instead of relying on air-conditioning), maple floors with all the marks of the building's history preserved and a spirit of simplicity revered by Quaker tradition.