third grade thing?

[thedaffodils]

Hi!

Could someone please tell me what 'third grade thing' refers to? Is there any say about 'second grade thing'?

Thanks!

Susan: I was just wondering how you'd feel if I went out with Bill.

Eddie: What?

Susan: Bill asked me out

Eddie: Bill? My Bill?

Susan: Well,see, that's the thing. He doesn't think of himself as your Bill. He said that date was just a one-time thing which I know, because when he asked me out. I told him I thought you guys were involved.

Eddie: So you haven't agreed to go out with him?

Susan: No. I wanted to check with you first.

Eddie: Wow that's nice of you.So, can I?

Susan: So, can I?

Eddie: No.

Susan: Why can't I go out with him?

Eddie: Because I saw him first.

Susan: That's a really third-grade thing to say.

The dialogue I quoted is from American soap opera--Desperate Housewives.

[Anglika]

It means "childish". I don't think the grade really has any importance.

[thedaffodils]

It means "childish". I don't think the grade really has any importance.

Thank you for your answer, Anglika.