The requirement for men and boys to swim in the nude was not confined to the YMCAs and private boys schools. As you can see from the photos in the media section of this group, junior and high schools that had pools were also frequently required boys to swim in the nude, as well as boys swim teams in competitions. All that came crashing down when mothers of sons who were shy and modest about swimming with other naked boys began protesting to their school boards that the local laws needed to end the male nude swimming requirement. Angry moms on the local level at first were the persuasive motivators to stop the practice of forcing their sons to swim in the nude.
No, that was not in my experience at prep school whatsoever. We had an indoor gym with an Olympic-sized pool. We were required to swim in the nude. However, our football, basketball, baseball, track, wrestling, and soccer teams played in uniforms, not in the nude. Such rumors are pure hogwash.
Your school being one of them doesn't mean it didn't happen elsewhere.
I was not referring to games or meets, just practices and gym classes.
I have seen quiet a few mentions of it on this and other sites.