Most of our classrooms have 5-wire component video cables (aka 5 BNC) from the podium (or equipment rack) to the projector. To upgrade the classrooms so they work with digital video we (well, facilities and contractors) had to pull out these cables and replace them with something more modern.
Atlona, Gefen and a few other manufacturers have come out with extenders that let you run digital audio and video over the existing 5-wire component video cables, thus eliminating the need for wiring upgrades. We’ll be testing how well these work, and we hope to find that it will speed-up classroom upgrades!