My dad was an Army officer. Brother and I attended crappy Army schools in Germany and Italy (Army schools = big city ghetto schools) before parents sent us to prep school. Andover for me and Exeter for my brother.
I experienced amazing culture shock. Andover was sinf or swim. My classmates were, for the most part, smart. Only dumbasses on campus were the PG year jocks being groomed for Ivy football and hockey teams. I got clobbered by how fast classes moved, by how difficult the tests were. I'd been a straight A student who wrote papers and studied for tests on the morning school bus ride. If I didn't turn something in on time, teachers accepted my excuses.
Now I was at a place that didn't coddle or hand-hold or accept excuses. If you copped an attitude or acted like an ass, Andover might well ask you not to return for the next term. I was in classes with 8-10 students, all smart and prepared. I nearly flunked out before gaining my footing. I needed an entire first term to learn how to study, how to take notes, how to write a sentence, then a paragraph, and finally an entire essay. Brother had similar experience at Exeter.
Andover provided me with a first-rate education. It forced me to grow up and stand on my own feet. If nothing else, it made college a breeze. Made some amazing friends. (Amazing how often the New York Times mentions my classmates. I recall reading that a guy in my dorm during senior year had inherited a billion dollars.)
The downside: I was clueless when I arrived at college. I'd gone to debutante parties and crap like that but I'd never had a girlfriend or even been on a date. (I'd managed to get laid but not at Andover.) I didn't own a car and barely knew how to drive. Knew more than was good for me about drugs and drinking. Andover was a school were students invited one another to cocktail hours before dinner. It wasn't until I got to Wall Street that I saw as much cocaine as I'd seen years before at Andover.
There was lots I disliked about the place. But I was a teenager and had my issues. Most of what I disliked about prep school probably had more to do with me. I would have been just as unhappy had I stayed at that Army school in Italy. So I don't blame Andover for anything.
And I generally had a good time.