When I was a driver's Ed teacher, I told my students that the horn was the least used tool for most drivers. It's one of the best things to use and NEEDS to be used way more often! If they wouldn't honk, I would do it for them (if it wasn't a dangerous moment, of course). Drivers are especially apt to cut off drivers' ed cars to get in front of them, so I would warn them and tell them that they should honk if someone is making things dangerous for their driving.