Kid who comes in regularly: How come you’re working today? You’re not usually here on Wednesday!
Me: The other girl who works here needed the day off so we swapped.
Kid: Oh no! I thought she was a boy!
Me: Nope, she’s a girl.
Kid: She looks a bit like a boy.
Me: Yeah, that happens to some people, but she’s a girl.
Kid: Are you sure?
Me: Yep, she told me she was a girl when she started working here.
Kid: Oh, okay! She’s nice. She gave me a lollipop once.
It was seriously that simple. Give kids the benefit of the doubt.