MIT has been using magnetic boats in their shore school for decades but Gary Bodie popularized the concept among team race coaches just a few years ago. We use two sizes; six inch boats for the blackboard in a large classroom and two inch boats for the little white board in our boathouse. There are two teams of three boats, red and blue, with full magnet bottoms, an RC boat, buoys, and a wind arrow. We use them for team racing situations mostly but, also for rules and tactics in fleet racing. For consistency, we always have the good guys in blue (one of our school colors) and the bad guys in crimson, I mean red.
Besides having the cool magnetized boats, we have several sets of cut out boats from cardboard. In fact, I just asked every skipper on the team to make their own set for problem solving. I doubt anyone did, but if they had, they could teach their less experienced crews during dinner. They might find their crews have more insight than they think.
An addendum to coaching tip VI-phone lists, include e-mail addresses (thanks Adam). On coaching tip IV-draggable anchors, I got many suggestions for inexpensive buoy anchors but a few missed the point. The buoy anchors need to be of such slender profile that they can be dragged at 20 knots without resistance. That is way chain or iron window weights work so well. Also, a couple of chain links two feet below the surface would reduce the chance of fouling centerboards (thanks Fran).