We had exactly the same poem in the school where I used to teach in Amman, Jordan. It was also on headed paper and began in typical Dahl style:
"Gorgeous Wendy (former headteacher) and all the lovely children at the International Community School" - then the poem and his signature.
Sadly, over the years, this little gem had been forgotten. So, just before I left the school this summer, I retrieved the poem from its dusty hiding place and had it reframed.
Although we now know "our" poem is not unique, it has pride of place in the school foyer for everyone to enjoy. As the school population comes from at least 40 different countries, Roald Dahl's humour will continue to make people laugh around the world!
Alison Johnson Zion Place Church Lane East Harptree Bristol