This is disappointing.
Impossible to tell the cause, however.
Could have nothing to do with the liberalization of the SSPX.
Could be as you state in the OP.
That these girls were not afraid of being discovered is interesting (I.e., apparently they are not made to feel uncomfortable behaving like this in St. Mary's).
Well done girls: Set the boys' passions on fire, and blame them for not being able to control themselves once they are made enemies of God, just so you could act and dress like them.
Would love to know who has told you this is OK.
Minimally, this reflects poorly of the fathers of these girls. Manly activity in manly attire.