All schools in Wales will have a school council allowing pupils' views to be heard, following new legislation.
Tredegar Comprehensive's council voted to change the uniform
Wales is the first part of the UK to make the councils a compulsory part of school life, after legislation was passed by the Welsh assembly.
Many schools already have councils which give their views on a range of issues around school life.
The Children's Commissioner for Wales, Peter Clarke said he was pleased that children had a greater voice at school.
School councils will be able to give their views on school life ranging from the uniforms children wear, to the kind of food served at mealtimes.
At secondary level, two representatives from the school council will be able to sit on the school's board of governors, but they will not be able to take part in discussions about disciplinary issues or matters concerning individual children.
Welsh Education Minister, Jane Davidson, said: "Many young people don't feel that school is an environment where they can have their own views heard and what we are doing with this legislation is making sure their views are heard.
"The head and the governing body are now required by law to listen to the views of the pupils."
Pupils at Tredegar Comprehensive School in Blaenau Gwent have had a school council for nearly six years.
It used its school council to bring about a change to the school uniform.
Head girl, Kayleigh Bennett, said: "The school council did a survey about what kind of school uniform people wanted.
"Lots of people said they wanted black and that's what we now have."
Head teacher Anna Foote said the council presented a sound case for change.
"The council said the will of the school was that they wanted a black jumper, they saw it as part of quite a smart look they wanted to design.
"I don't know a head teacher in Britain who would argue with that idea."
Many European countries including the Netherlands, Germany and Sweden also have compulsory school councils.