It was due to my funny accent, as we had moved abroad during my formative years, and I was speaking another language when we moved back a couple of years later.
It all ended when I beat the living crap out of one bully. He was a small guy, and I was already a head taller than most in my class. I just blacked out, and used him as a punching bag after one of his regular snide remarks.
He ended up in the hospital with both eyes glued shut, broken nose, and concussion. Teachers and parents were shocked.
But I was never bullied after that.
I don't advocate violence, but for me, that's unfortunately what worked.
(In a interesting twist of faith, years later I actually ended up becoming good friends with some of the bullies, because of shared hobbies, and them maturing)
I remember confronting my bully in primary school - he stopped after that.
But my friend from secondary school who one day finally snapped gained nothing from his confrontation.
Edit: sorry, that was an unnecessary response by me. Clearly you weren't thinking in those terms. Apologies.
[0] https://www.amazon.com/Adult-Children-Emotionally-Immature-P...