Yep. Unless they get all of their sycophants to gang up on you and do charming little things like getting everyone in your class to talk about a party to which everyone but you was invited whenever you're present. Unless they sneak in and steal your personal belongings, destroy them, and leave them hanging on a fence. Unless they threaten to follow you until they get you in a secluded place where they can freely beat the snot out of you.
Yep, standing up to them works every time. Except, that is, when it just encourages them to ratchet up the bullying. Bullies almost always have sycophants who follow their lead. Victims almost always are loners. Bullies need to be told by authorities that their behavior will not be tolerated, and victims need to be encouraged to report such behavior. And the behavior needs to be punished.
Standing up to the lone bully, that almost nobody likes, could well work.
When bullying has gotten organized into a gang, things are dicier.