I was in Fifth grade, and somehow our class had a few tadpoles- maybe 2 or 3?-in an aquarium. As time went on they naturally changed into frogs. One of the students pithed and dissected one of them, with the teacher's permission. Most of the students were crowded around, watching, but I stayed away. I wasn't very upset or crying or anything- my family fished, and Dad sometimes killed fishes he had caught to eat, so I was somewhat desensitized to it. I still just thought it was wrong. But looking back, I know exposure to this and other forms of animal mistreatment lowed down my progress through pescatarianism and vegetarianism. But on the other hand, I knew a vegetarian neighbor- an elderly gentleman- and had positive experiences with cats, dogs, squirrels, and various animals at a game farm / petting zoo near my home town.
I don't know. My social environment when I was growing up was what it was, and my inherent tendencies were what they were. I think I ultimately went veg from a combination of my exposure to loveable animals, something inherent in myself, and my family/friends/associates. But I can't help thinking that I might not have been able to do it if I had grown up in a subculture where animals were routinely mis-used- such as one co-worker who grew up on a farm where his family routinely slaughtered chickens, pigs, and cows.