In fifth grade, I went up to my rebbe and privately said that I was able to make it thru half the davening with full kavanah. Instaed of offering chizuk, he publicly embarrassed me in front of the whole class for not davening the whole daven ing with kavanah. Guess how much kavanah I davened with the next day.
In high school ( in the 1960’s )as freshmen, many boys had questions, which were asked in a respectful manner. Our rebbeim, who came from pre-war Litvish yeshivas, could not imagine that boys in high school would have such questions and assumed we were being chutzpanik and responded in kind. After 4 years of this, many of the boys were barely frum.