Something just came across my mind today... do you generally tip your ski instructor in Switzerland or anywhere else in Europe for group lessons or private lessons?

In the states, especially at the big resorts out west, it's pretty normal and often expected to tip the instructor for private lessons, and sometimes even groups as well. But since tipping is so common in the states for just about everything, I am not sure what's the standards here in Switzerland and what's expected from the instructors. Anyone?

It's hard to decide. I mean, you certainly don't tip your piano teacher or your tennis coach, but I can also see why you would tip a ski instructor instead...