If someone repeatedly mis-used (expensive) supplies, I'd probably tell them after free replacement #1 that they would have to either make do, or buy another kit. That's a tough one to call, however...you have not only that person, but the whole class watching your demenour.
Your absolutely right in the fact that every student is watching your every move and these could be future clients, students whatever. The rest of the students in this particular class even remarked about how patient I was with this lady after she left the class. What am I going to do? Have a drink or 10 after class. lol There is so much networking now a days and hopefully for those who want to participate that my former students spread the word around. Most of my students though are really nice for that matter. It's so nice to see the excitement on there face when they finish a project and then they walk of class with something special they made with there own two hands for themselves. I actually have students from that class coming to my new class. This absolutely important if I want to expand on my teaching. I really need to build and excellent reputation.



I don't know how you have the patience for it - especially that tiny stuff you do - omg..