1 {scene: the Hawkins Middle School A.V. Club room, where the science teacher Mr Clarke is showing the kids something after school}
1 Mr Clarke: It came. The Heathkit Ham Shack. Ain’t she a beaut?
2 Dustin: Wow. I bet you could talk to New York on this thing.
2 Mr Clarke: Think bigger.
3 Lucas: California?
3 Mr Clarke: Bigger.
3 Mike: Australia?
4 Dustin: {sitting at the receiver} ’Ello, this is Dustin Henderson, Hawkins Middle A.V. Club. Do you eat kangaroos for breakfast?
4 Mr Clarke: You have to turn it on.

I don't think I've ever eaten kangaroo for breakfast, although it's very possible that I have and just don't remember it. I know I've had kangaroo for lunch and dinner.

When I saw this scene in Stranger Things, I assumed "A.V. Club" was short for "Audiovisual Club", but I had no idea what the "visual" side of things was. Audio obviously encompasses shortwave radio, but I was at a loss for the visual.

Google to the rescue! It turns out that AV Clubs were a common thing, at least in schools in the USA, and they involved students who were into technology learning how to do things such as operate slide projectors, film projectors, and audio gear such as the public address system. The teachers could then rely on the kids in the Club to assist when using such equipment in the classroom.

This was never a thing here in Australia, as far as I know.