I don't know about you, but I was taught "stop, drop, and roll" relatively early on*. Also, the reflex save to put out flames doesn't require any special procedure: rolling on the ground, or smothering with a cloak merely gives a +4 bonus on the save.
*(I have not, thankfully, yet had the opportunity to use that knowledge, but I feel like I would remember it if there wasn't a water source at hand.)
Of course, I don't know whether the average child in dnd-land would be taught what to do if he's set on fire.