Define "important"

Me: Nick, is this important? I'm in the middle of teaching a 2nd grade class.
Nick (4th grade): Yes. Very important.
Me: Ok, what is it?
Nick: I found this leaf. It is shaped really weird.
Me: Um. Why don't we take a look at that later.
Nick: You think it isn't important?
Me: No... not that... it's just that... it's so important we need lots of time to look at it. Yeah.