You are making up your own norms, Sean. Again, please point to a Church teaching which precludes women/girls entirely from athletic endeavours.
As far as modesty, you know, right?, that in the early Church women were baptized by immersion and either nude or close to it. That was the original role of the so-called (non-ordained) "deaconesses". They would assist the women being baptized while the bishop would stand behind a screen so as not to see them while he pronounced the form of Baptism. So, again, given the stipulation I laid out that the girls should not dressed that way in mixed company or out in public, the perfect modesty required when in the presence of the opposite sex does not always apply.
If the girls were to, say, play volleyball at an all-girls' school in the gym, in an intramural (not-particularly-competitive) manner, I don't see anything wrong with that.
Yes, yes, I’m making stuff up. Everyone knows the Church has no problem with high cut revealing attire on women, manly attire on women, makeup, or whatever else feminist liberal Americans want to push through on the pretext it hasn’t been infallibly condemned.
Why, if the BVM were alive today, she would wear pants, play field hockey, and slap on some makeup before heading out for girls night to impress the other girls.
BS!
For someone so severe in other areas, your liberal-laxist-feminist views in this area are rather surprising.