It’s gym class and you’re completely naked. You could be having a bad dream — or you could have just been a male student in a Chicago Public School swim class.

For more than 50 years, high school gym classes in CPS required boys to bare it all during swim instructions — a policy commonly used across the country. Curious City reporter Monica Eng recently dove into the history of this policy after numerous Curious City fans asked about it. (You can hear the audio of this feature on Thursday during All Things Considered.)

Eng shared her findings with Morning Shift host Tony Sarabia, and we heard from callers who recounted their experiences in swim class. Here are some highlights.

What was the policy and when did it start?

Monica Eng: The policy was the boys swam nude and the girls had stretched-out tank suits.

When it started? It’s harder to date because Chicago Public Schools — I started asking them in April, then May, June and August. They will not talk about it. So I don’t have official dates. I did interviews with coaches and crowdsourcing, and it appears it started around the 1920s when they were starting to build a lot of pools in big cities across the country, including in high schools.

Swim class for some girls wasn’t so easy

A caller named Gale shared this story about going to swim class at a high school in suburban Deerfield during the 1970s.

Gale: We had the intimate Ms. Olston, who I’m still haunted by, who was the girls’ locker-room inspector and bathing-suit hander-outer. And inevitably you’d walk through the showers, take your shower, and then you had to stand in front of her, show her your frontside and then your backside, and she was making sure you were clean.

Then she’d size you up for one of those tank suits, and I remember they were, like, light orange and light green, so I still hate those colors. And she’d inevitably give you a suit that was too small for you, so you’d be spilling out of it.

Boys were also inspected

A caller named Stan, who said he graduated from Lake View High School in 1971, said the experience of swimming naked was traumatic.

Stan: Not only did you have to swim with nothing on, but when you were going out to the pool from the shower, the coach would be standing by the door and …

Eng: Inspecting you?

Stan: Yeah, and can I tell you what he used to call it? It’s just really embarrassing. He would call it “checking the lint trap.”

Tony Sarabia: Was this a traumatic experience for you?

Stan: You know, it was. After that — that was my freshmen year of high school — I would do anything to get out of having to take swim class.

‘It was kind of comical’

John, who said he graduated from Lane Tech High School in 1979, said he is surprised by the reaction the policy receives now.

John: It was the policy throughout my tenure in high school. At the time, it was a little strange, but I think the way people look back on it now seems almost bizarre. There’s this sense of horrorification about the whole thing, and it just seems like we’re in a kind of new era of puritanism, where this whole episode is looked back on as something that just can’t be believed.

It was kind of a comical thing among most of the students I knew at the time. And I think the rationale for keeping dirty suits out of the pool was given. We always thought there was an ulterior motive that some of the coaches were on the pervy side, maybe, but that was just a joke among us.

But the whole thing, I don’t recall being traumatized by it all.

Freshmen hijinks

Elle said she went to suburban Highland Park High School and remembers how she learned of the nude-swimming policy.

Elle: My girl friend and I, we were freshmen, and so we were new to this school. And during one of our free periods, we decided to roam around and explore the school. So we came upon the boys’ pool and the doors were locked, but we could hear voices. So we were peaking through the slits in the door. I looked first and I was like, “Oh my God. Patsy, they’re naked.” So Patsy, she pushes me aside, and we were mortified and ran away giggling.

Eng: This was the fear of every 14-year-old boy, that this was actually happening.

This interview has been edited for brevity and clarity. Click the “play” button to listen to the entire conversation.