I dropped out of high school for the same reason, I had a teacher that failed me for writing an essay in three different styles of handwriting, and it just broke me. I wasn't a particularly good student, and I especially had a habit of just not doing essays, but I was making an effort to make it through the humanities and get my shit together, and to have that effort rewarded with a 0/100 just made me view the entire system as an absolute joke. I have a more nuanced take now, but it's still impossible to wrap my head around how comfortable people are with the education system here.
Society is made of people, people! You live in a society. Why do we not want the foundational atoms of it to be the best they can be? It just seems so obvious and simple and non controversial.