Speaking to The Guardian, Nicholls summarised what many believe the problem with the sentence to be – namely, the sexualisation of breasts, which is already an issue in so many cultures across the globe.

Stating that the sentence was “extremely problematic”, she said it “reinforces the sexualisation of breasts, which makes girls and women self-conscious”.

“The other huge issue is the false equivalence of developed breasts with attractiveness and being ‘grown-up’,” the teacher added.

“The ‘grown-up’ statement is troubling. There are girls of 13 with developed breasts. To describe them as ‘grown-up and attractive’ would be worrying, as would infantilising an adult woman with smaller breasts.”

And even if the book’s author was attempting to somehow reference the idea of 'attractiveness' as an evolutionary reason, it is a woefully misguided passage to include in a book for young boys.

Following the onslaught of criticism, a representative from Usborne told The Guardian, “Usborne apologises for any offence caused by this wording and will be revising the content for reprinting.”

But, as one Twitter user pointed out, the publisher could take another step: “Good that Usborne have listened, apologised and responded to the criticism… Great if they recalled existing stock.”

Images: Usborne

Puberty guide causes fury with “extremely problematic” explanation of breasts