Doors by Carl Sandburg

An open door says, “Come in.”
A shut door says, “Who are you?”
Shadows and ghosts go through shut doors.
If a door is shut and you want it shut,
why open it?
If a door is open and you want it open,
why shut it?
Doors forget but only doors know what it is
doors forget.

Check out Lemony Snicket’s article on the Poetry Foundation where he points out that sometimes poems for adults (like the above) work well for kiddos…
“If you are a child, you might like these poems. Of course, you might not. Poems, like children, are individuals, and will not be liked by every single person who happens to come across them. So you may consider this portfolio a gathering of people in a room. It does not matter how old they are, or how old you are yourself. What matters is that there are a bunch of   people standing around in a room, and you might want to look at them.”