Coco Chanel once observed that “a girl should be two things — classy and fabulous”. Now a leading girls’ school has added a third: a girl should no longer be called a girl.

Sally-Anne Huang, head­mistress of the private James Allen’s Girls’ School in south ­London, said last week she had changed her vocabulary in recent years to try to avoid causing offence to teenagers querying their gender identity.

She said: “I try not to say ‘girls’, [but] when you have been teaching for 20 years it is very hard not to say ‘girls’.” Instead, she tries to use the term “pupils” and the pronoun “they”— in place of “she”— to be sensitive to the feelings of transgender students.

Pupils are allowed to wear ­trousers,…