I will go first. When I was 14 my teacher noticed I have a knack for literature: analyzing and interpreting texts, understanding the meaning of poems, imagining plays I read immediately on stage. He did not actively mark me down in my tests but he demanded for sure more from me than from my classmates for the same grades. Essays I handed in he would give back to me, instead of a grade I would find marks and comments on where I should dig deeper or think further. It was challenging. It trained me.
I joined the school's theatergroup at the same time and while my acting skills are abyssmal, he would ask for my opinion on choosing costumes, choosing roles for the actors, which play to do next, how to give instructions. More training, analyzing the play, putting it on stage.
I noticed how far ahead I was in reading, studying literature, analyzing texts and writing essays by the time I was 17. Getting my diploma was a walk in the park.
Went to uni, studied philosophy, history and literature, still way ahead of the other people in my classes.
He demanded more from me than everybody else in class, knowing I could deliver. He trained me, honed my skills, gave me a huge advantage later in uni. I studied what I studied because he showed me the fun in literature, the satisfaction one can get when cracking a difficult text and notice the little details that make a piece of literature awesome.