Boys will be allowed to wear skirts at school from September, as a new gender-neutral uniform policy comes into force in Wales.
The new statutory guidance from the Welsh government includes not assigning a gender to items of clothing, such as trousers and skirts.
Education minister, Kirsty Williams, said: "We should not be enforcing outdated ideas of what clothes are suitable for their gender, especially if it makes them wear something they feel uncomfortable wearing.
"This new guidance makes clear that school uniform policies should not dictate items of clothing based on gender."
A consultation was launched on reforming uniform policy in Wales last autumn, following the summer heatwave.
During the consultation, respondents backed the introduction of the gender-neutral uniforms.
One wrote: "This should include the choice for all children as to whether they wear trousers or skirts, regardless of their gender assignment or sexuality."
Another said: "The question of gender of a school uniform should be addressed by allowing those pupils with gender fluidity to wear either gender of uniform as required, without discrimination."
The new uniform policy also addresses the cost and accessibility of the garments.
Governing bodies being urged to consider whether school logos are necessary, and whether items could be bought from more than one outlet.
They will also have to consider whether there is a need for different uniforms for summer and winter.
The Welsh government currently provides £125 for students eligible for free school meals to buy uniforms and other equipment through the pupil development grant.
Eligible Year 7 pupils are also entitled to a grant of £200 to help with the costs when beginning secondary school.