All of the kids in my daughter's class have started calling their male teacher by his first name. It's actually a slight nickname. The teacher is okay with it, I guess. He hasn't told the kids to stop. But he's not that type of guy. Our daughter came home this week and called him by his nickname and we told her we expect her to call him Mr. X and explained why.

If all the kids in class were calling a teacher by his nickname (like Timmy) would you be ok with your child doing so?

EDIT: This was kid-initiated, not something that the teacher said they should do. The other teachers/administrators/parents call him Mr.