Excitements at the Chalet School

I was reading Elinor Brent-Dyer's Excitements at the Chalet School tonight (which doesn't live up to its title, btw), and thought to look at the cover art. As I've mentioned before, I'm not terribly visual, and I have to remind myself to look at images instead of words.
It turned out that this image was fascinating. There is a performance in Excitements, but it's a panto of Aladdin. So why are they dressed in coolie hats and classical tutus? Why are two dancers en pointe? It's often unfair to criticize book jackets too closely, because often the illustrator didn't have access to the text. But here, I can - and did - find the exact paragraphs that the cover is meant to illustrate.
It turns out that the coolie hats and the odd chinoiserie are Brent-Dyer's fault. Why on earth set Aladdinwith a Chinese background? No idea, but she did. But the illustrator took several characters off the stage for the scene on the cover, and made the Chorus (the ones in the coolie hats) have a very Balanchinian hip thrust to match their pointed front feet.
Brent-Dyer, with her usual clarity about ballet, described how the ballet dancers "swirled in a mazy dance." Clearly, her ballet dancers are not really ballet dancers - in The Chalet School in the Oberland (1952), Brent-Dyer gets quite enthusiastic about having two girls in the school who have actually had dance training. But they wouldn't still be there in this book. So how did Chaletians - even ones from the finishing branch of the school - wind up en pointe in the illustration? In a school where no one dances seriously at all, let alone en pointe? In dance clothes that not only don't match the panto's theme, but also would have been a bit daring for schoolgirls performing in public in Switzerland at that time?
Well, other authors were writing about ballet and horses by the late 1950s, because the market for school stories was dwindling (or was it? Check out Rosemary Auchmuty's A World of Girls and A World of Women, if you're curious about other reasons that publishers might have been less willing to publish books about all-girl schools).
So I suspect that the publishers - or the illustrator - saw that the panto included a ballet, and got excited. Even though the book really isn't about the ballet, or even the panto, the illustrator drew ballet dancers. I imagine there were some disappointed readers who'd bought the book for its cover!