I'd be very surprised if that was explicit and in writing. Having been exploited by teachers at university, I'm sensitive to this kind of thing. Your students are not there to make stuff for your benefit. It seems to me like you're exploiting them.
Sure you have the right to believe what you want. Maybe youre used to a shithole country like america, where people are more exploited.
The schools apprentice makes whatever we tell them. They are in unions and have the same rights as everyone else. And the same rules goes for our workshop as everywhere else in this country.
P.S. the gifts I get from my students also tell me how miserable they are.