In your first sentence did you men to write "unfair?" I hope so!
You think girls high school sports are unimportant because... why? Girls high school sports don't matter? Boys aren't going to take away scholarships if they aren't taking female hormones?
Let's face it, most people don't even get an opportunity to play college sports. High school is the highest level most kids will get to compete. So the boy will be "happiest," as you say, running and winning against girls. But who is asking the girls what makes them happiest? The girls are being told that the happiness of boys supersedes their right to fair play and an honest opportunity for athletic accomplishment at the high school level.
Then, what if he decides to use hormones? Then it's somehow OK? It is still unfair to women and girls.There are more and more cases of boys being allowed to compete against girls, slowly normalizing this form of cheating, so that it will be easier and easier for the next boys who try to horn in where they do not belong. (For example did you know there are three -- count'em three -- all-male "women's" bike racing teams on the cycling circuit?) Whether they mean to cheat or truthfully believe they are female -- it doesn't matter. They're male and this alone disqualifies them from female sports.
No one takes women and girls seriously in sports. When people start debating this issue, it is often women/girls who are protesting and men/boys saying it doesn't really matter, and who are ready to hand girls sports over to boys. Men are more often hold positions of power in the governing bodies that make these ridiculous rules, saying that because males can be "sort-of female-ish," that makes it fair for them to compete against actual females. Men, we need your help. Please stand up for girls and women's sports. Stop saying high school sports don't matter. They matter so much to the kids participating in them. Even if high school sports are not going to result in a scholarship, prize money, fame, a lucrative endorsement deal -- high school sports matter so much to the kids who are participating. For many, it's their last go at competitive sports.
Women and girls have so few opportunities in sports as it is, while there are ample opportunities for men and boys. Please help us females hang on to what little we have. Please speak up so that males must compete in male divisions, and females only compete in female divisions.