a membership at the 'gym' = a 'gym' membership
Students are required to take 'gym'.
He works out at the 'gym'.
(..) Sir, we've searched everywhere. There's no sign of them. Nothin'. Keep it locked down. All right. Kitchen. How did they find us? I don't know, but they knew we were in the gym. Lando. - Got 'em! - Go, go, go, go, go! Come on! - There they are. Freeze. - Back! Go back! Go, go! Go left! El! (..)2016 TvShow: Stranger Things Title: Chapter Eight: The Upside Down Season: 1 Episode 8
(..) Friends don't lie. Well... I was thinking... I don't know... maybe we can go to the Snow Ball together. - "Snow Ball"? - It's this cheesy school dance, where you go in the gym and dance to music and stuff. I've never been, but I know you're not supposed to go with your sister. - No? - I mean... (..)2016 TvShow: Stranger Things Title: Chapter Eight: The Upside Down Season: 1 Episode 8