Teacher teacher!
Why? What do you call your teacher? “Teacher?” What, are you in kindergarten or something? If so, maybe you should get off the internet and go play outside. I’m just kidding, I know that in some places in the world, students actually call their teacher “teacher” instead of by their name.
In the US, we call our teachers Mr. or Ms./Mrs. [Insert Last Name Here]. That’s not too strange, is it? We use the title Mr. or Ms./Mrs. along with their last name to show respect. Calling a teacher by their first name is unheard of and incredibly rude, even after you graduate.