The Day Our Teacher Went Batty, by Gervase Phinn, Puffin Books, 2002.
I'm not sure where I picked up this little book. Or when. I do know the "why", though. I picked it up because the humor seemed charmingly British -- Yorkshire, in fact.
So, however long it has been sitting on my shelf, I read it last week when I was feeling quite "poorly". I can't say I loved, or even understood, every poem in this book, but the poems I loved, I loved very, very much.