Betsy Ross, kids go through different phases as they transition through puberty from a child to an adult, during which there's a lot of potential for gender confusion. Girls are commonly known to engage each other intimately, as a precursor to engaging boys, but boys will also (less commonly) sometimes experiment with each other before finding the courage to approach girls.

It gets more complex since girls can begin puberty as early as eight and as late as sixteen. Boys start as early as twelve and as late as eighteen. During the process an adolescent's preferences for one sex or the other can swap multiple times before his or her identity (as gay, mostly gay, bi, mostly het or het) is established.

(And then adults can change their minds, and often do, but that's a different topic.)

During the developmental years of puberty, kids often get discovered in their activities, and often branded based on the circumstance, not just because we're homophobic as a society, but because we're erotophobic as a society, and are terrified of our kids growing up at all, let alone into something aberrant. Hence, a trio of boys caught circle-jerking can be branded as fags long before any of them have any idea who they are or what they like.

It's the American way.