The Scottish Liberal Democrats have backed a motion calling for all schools to have gender-neutral uniforms for students.
Jess Insall, 15, told the party conference that allowing girls to wear trousers and boys to wear skirts could result in happier students, better exam results and even better jobs.
She said: "It's a small step forward but it will make a huge difference."
Her call was backed by the party's UK deputy leader, Jo Swinson.
Ms Swinson recalled how she had campaigned for girls to be allowed to wear trousers when she was a student at Douglas Academy in Milngavie.
She said: "There is an important principle here about not segregating boys and girls according to gender.
"There's also practicalities. I read about a school where primary school girls were told they weren't allowed to turn cartwheels in the playground because it was 'unladylike'. As if we send our little girls to primary school to learn how to be a lady."
'Harmful gender stereotypes'
Party members at the conference backed a motion calling on the Scottish government to require schools to provide "inclusive, non-prescriptive gender-neutral school uniform policies".
In her speech at the conference in Dunfermline, Jess hit out about the "harm that sexist uniforms are doing to young girls".
The teenager said: "I'm not telling anyone to take away their skirts, I'm telling you all that pupils should have the freedom to dress appropriately for their personal identity regardless of their gender."
She added: "Is it really acceptable that we dictate the way our children dress based on only their gender - or in many cases the gender that society forces them to conform to?"
She argued that giving girls "more practical uniform options" could help encourage greater physical activity, and spoke out about the "harmful gender stereotypes that sexist uniform policies promote".
She said: "The minute a girl walks into a primary school she is shown that the boys have more freedom to run about, she is told while she has to wear a skirt the boys don't, she is told to take inequality for granted and to respect it as the norm."
"Gender-neutral uniforms will make a real impact on pupils' school lives. When pupils feel comfortably and appropriately dressed it boosts self-esteem.
"This in turn boosts mental health, which means pupils will be happier and more productive in schools. This leads to better exam results which can lead pupils to better jobs."
'Political car crash'
During his speech at the conference, the party's Scottish leader Willie Rennie said the Liberal Democrats should lead a national debate on the benefits of immigration.
He said any loss of EU citizens after Brexit could have a devastating economic impact and called for politicians who "blindly back Brexit" to be sent home, rather than EU citizens.
The Liberal Democrats campaigned to keep Britain in the European Union in 2016, and now want a second referendum to be held once the terms of the Brexit deal have been negotiated.
Mr Rennie told the conference that the Conservative government at Westminster would either "betray Leave voters" by back-tracking on promises to cut immigration after Brexit or "trash the economy".
And he used his speech to urge people across the country to "stand up for immigration".
Predicting that a "real political car crash" is on the way, he added: "If immigration is not cut with Brexit then Leavers will feel betrayed because that is what they voted for.
"If the Conservatives keep that promise, and immigration is cut, it will damage our economy and public services, and even more will feel betrayed because they were not told this would happen."
Voters in the EU referendum were not told the price of cutting immigration, Mr Rennie said.
He added: "The price is a shortage of workers to get food from British farms into the shops.
"The price is a shortage of carers, nurses and GPs. The price is billions of pounds of lost taxes from these jobs. They are already going home and Brexit has not even happened yet.
"Some say that too much immigration is a threat to our way of life. But the truth is that not enough immigration is the real threat to our way of life.
"It's not the workers from Poland, Romania or Bulgaria who we should fear. We should fear all those political leaders who are blindly backing Brexit. These are the people we should be sending home."