One of the most effective teachers I had in middle school, in the mid-1970s, was a high-and-tight, no-BS former Marine Sargent.
He taught English and was head/coach of the drama and forensics departments. He was a stickler for annunciation, stage projection, clarity, concision, and proper grammar. He was also very empathetic and understanding. But when he shouted from the back of the theater that he couldn’t hear you or that he was falling asleep from boredom, you adjusted accordingly.
We regularly had to do public speaking in his class. Everyone was graded on all of the errors he/she made while speaking and also on those you noted and pointed out in others. It was sometimes humiliating, but as a student and thespian, I really learned a lot and respected his pedagogical methods. He didn’t make me want to join the Corps, but my grammar definitely improved.