Boys could be allowed to wear skirts at a north London private school if a plan for gender neutral uniforms comes in.
Highgate School is considering mix-and-match outfits for pupils after head teachers said that growing numbers of children were questioning their gender.
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.
Girls at the school can wear grey trousers, dark blue jackets and ties.
But boys are not currently allowed to wear grey pleated skirts, although they would be under the new proposed dress code.
"We are asking them, should it be called uniform number one and uniform number two?," said head Adam Pettitt.
He said the issue of a gender neutral uniform had come up during question and answer sessions with his A-Level students.
This generation of young people was really questioning the binary way people look at things, he said.
"We're therefore exploring how our uniform policy could evolve to cater for those who do want to match clothing to gender, as well as those who don't."
He added: "In common with all other schools and youth organisations, yes, we are seeing greater numbers of pupils questioning gender identity than in the past.
"Having said that, in years gone by, absolutely no young people were raising it at all and it seems inconceivable that these sorts of questions simply didn't exist.
"The fact that there is significantly greater support and information available, both in schools and elsewhere, means that young people need no longer feel afraid to ask questions or speak out about their feelings.
"If they feel happier and more secure in who they are, it must be a good thing," he said.
Mr Pettitt said parents would be consulted before changes were introduced, but acknowledged that some former pupils had written to complain the school was "promoting the wrong ideas".
Co-educational independent boarding school Brighton College, where Mr Pettitt is a governor, has introduced a similarly gender neutral uniform.
Student equality groups have called for teachers to observe gender neutral speech codes and for a ban on phrases such as "man up".
And figures show a sharp rise in the number of young people seeking help to change gender.
Highgate School is holding a conference next month called The Developing Teenager which will examine how teachers should approach issues raised by transgender and gender neutral students.
In 2011, 12-year-old boy Chris Whitehead wore a skirt to school because he was angered by rules at Impington Village College, near Cambridge, that did not allow boys to wear shorts in hot weather.
The Year 8 pupil said he researched the policy, found a loophole in the rules and turned up to school in a skirt.
The school pledged to review the policy.
And last summer a group of teenage boys wore skirts to Longhill High School in Rottingdean, East Sussex after being disciplined for wearing shorts on a very hot summer's day.