Platinum catalyzes the oxidation of methanol.
This oxidation occurs on the surface of the platinum wire and causes the wire to glow red. Eventually it will get so hot that their will be a small methanol explosion. The oxygen in the flask is consumed in this explosion, thus stopping the oxidation reaction. The explosion is small and should not be dangerous, but wear safety goggles and set the shield between the flask and the students. The flask may get hot, wear gloves to protect hands.