Michael Rosen is an English poet and author who was the Children's Literature Laureate before the current incumbent Anthony Browne. Two of his books stand out in my early childhood library, but I'm sure that they are probably just as popular in other libraries as well. These books are We're Going on a Bear Hunt (illustrated by Helen Oxenbury) and Mustard, Custard, Grumble Belly and Gravy (illustrated by Quentin Blake and including a CD read by Rosen himself). I'm sure the calibre of the illustrators helps the popularity of these books, but even more so I think it is the rhythm of the words. Rosen has the gift of being able to write poetically without having to make everything rhyme. His poetry has much to teach children about what poetry is, is not and how much pleasure it can give. His poems are energetic, enthusiastic, cheeky, reflective, everyday and enjoyable all at the same time!
There is multitudes on the web about Michael Rosen and there are many more books to explore besides these two. A good place to start is his website and his performances on YouTube. And if you are at a school which isn't convinced about the need for a library and a teacher/librarian you have Michael Rosen on your side. Show this at a staff meeting.