When girls have boyfriends in high school, it is far more of a social trend rather than a close relationship in itself. I've tried saying this to girls but they just don't want to listen, don't know if it's voluntary or not.
But girls hop from one guy to the next only because they feel the slightest bit of affection towards them; whether this be awkwardly admiring them from afar or hugging them in public. I wish girls would actually think a relationship through instead of trying to get a boyfriend so they can fit in or something. After they get the guy, they hold hands and hug before class, then they start getting emotional when they break up, even though everybody expected it, then they're fine after 2 days. Repeat cycle.