Is it true that boys had to swim naked in swimming class at school/YMCA in the US in the 1960s/1970s and girls were allowed to watch?

I worked at a scout camp way back in the mid 70s, in Kent, in England. Every week there was a closed session at the indoor swimming pool for males only, to swim "Without the restriction of a costume"

"Closing" the pool did not extend to covering the windows at the fire escapes at both ends of the pool. There was usually quite a set of "spectators" of both sexes, around these. We tried to chase them away but people can be "strangely persistent" under some circumstances.

We discontinued the sessions after a couple of months.

Geez ! Where in the heck did you hear that? Totally untrue !

When I went to YMCA in 50's, to learn to swim, we were naked. But the YMCA was for men only, Girls/women were not allowed in the building. There was no problem with it,  The Y was the only place kids without lots of money could afford to learn to swim. I think the rule of no suits was so kids with no bathing suit would not be embarrassed about not being able to afford a suit.