Kind of surprising, because obviously Sappho as a queer symbol long predates this book, so it can't be entirely the case that 'it was totally innocent back then', as you'd often hear for this sort of thing. But apparently it was considered plausibly-innocent enough for a school story, at least!

The other alternative is Catullus' irresistible object of desire, which I also would not have expected to see in a school story!