Boys could be allowed to wear skirts at one of the UK's top private schools if it introduces a plan for "gender neutral" uniforms.
Highgate School in north London is considering mix-and-match outfits for pupils in response to growing numbers of children questioning their gender.
Student equality groups have called for teachers to observe gender-neutral speech codes and for a ban on phrases such as "man up".
The school, which charges up to £6,790 a term, has also been encouraged to allow unisex toilets and open all sports to all pupils.
Boys would be allowed to wear grey pleated skirts under a new proposed dress code that would be referred to only by a number.
Girls are currently allowed to wear grey trousers, dark blue jackets, and ties at the school, whose past pupils include cricketer Phil Tufnell and former Home Secretary Charles Clarke.
Headmaster Adam Pettitt told the Sunday Times parents would be consulted before changes were introduced.
"If they feel happier and more secure in who they are, it must be a good thing," he said.
"This generation is really questioning being binary in the way we look at things."
Highgate School is holding a conference next month called "The Developing Teenager" which will examine how teachers should approach issues raised by "cis", "trans", and "gender neutral" students.
Mr Pettitt said some former pupils have written to complain the school is "promoting the wrong ideas".
The number of teenagers seeking gender identity treatment has soared during in recent years, according to figures.
The Gender Identity Clinic at the Tavistock and Portman NHS Foundation Trust saw more than 2,000 teenagers last year, as opposed to just 100 when it opened in 2009.
The youngest referrals to the clinic were just three years old.
