Did you ever get into trouble at school for calling a teacher by their first name?
I remember doing that once in high school. It was a teacher I really liked. He gave me an evil look and warned me to never do that again. Why do some teachers get offended by that?
No, but some of my teachers in high school hated their nicknames. Sra. Gallego's nickname was Veronica Crabtree. I got into trouble for calling her that. Sr. Parker's nickname was Herbert J Garrison. He laughed about it. Dr. Suarez's nickname was Mr. Mackey. I don't think he cared.