Julie Richardson, headteacher at all-boy’s school Verulam School in St Albans, says big afros, long hair, cornrows and man buns are all acceptable at her school.
And while still having to dress smartly, students no longer have to wear a blazer and tie.
Previously, students could be sent home from the Hertfordshire school if their hair was deemed to be “extreme in style, colour or length”.
Watch: Teen exposes how 'sexist' school dress codes can be
But since taking over as headteacher last September, Ms Richardson has removed all reference to hair from the uniform policy.
She says such rules are outdated and do not fit with modern ideas on dress as well as unfairly targeting students of colour.
It comes after it was reported in December a 14-year-old school was removed from classes and put in isolation after going to school with his hair in plaits at Exmouth Community College in Devon.
Ms Richardson has now urged other schools to rethink their uniform policy.
She said: “It is utter madness to be taking children out of class, away from learning just because their hair style does not fit in with archaic ideas on dress.
“It is my view these rules, inadvertently or not, target students of colour, and are as such are not inclusive and discriminatory.
“This is not the type of school I would like to attend, work in at or lead which is why we have removed all reference to hair in our uniform policy. We want our boys to embrace how their hair grows.
“That means afros, long hair, man buns, cornrows, bleached, dyed, whatever way our boys choose to express themselves is OK by us.
“Too many young people feel that they need to look a certain way and conform. This is fuelled by social media. We want our students to know it is OK to be themselves.”
The school has also done away with sombre business attire for sixth form allowing students to dress professionally but with greater choice.
This includes cultural and religious dress such as ankle-length thobes which are commonly worn in the Middle East.
Ms Richardson added: “If business men and women in the City are no longer wearing suits and ties why should teenagers in sixth forms?
“It’s about having the choice from a list of things deemed professional rather than insisting on one type of clothing.
“Most schools insist on this strict uniform policy but cultural or religious dress is rarely mentioned as being acceptable.
“They have vision statements claiming to be inclusive yet their policies are anything but.
“It is about having helping students have a positive self-image and mental health. This is what is important for us.”
Students have warmly welcomed the changes. Student Wasif Rashid, 15 said: “The changes have allowed students to be free to express themselves, embracing who they are.
“We feel accepted and included in the school community and decided to wear our thobes to show this.
“Being able to wear one in the sixth form is something that makes me feel I can be myself and that my faith is being respected.”
Watch: Students outraged over school dress code policy