A public consultation will go ahead over plans to open up Notre Dame High School in Dowanhill to boys.
Glasgow City Council rubber-stamped the exercise (Thursday) after a campaign by West End parents.
Notre Dame High is the only single-sex state school in Scotland.
It takes many Catholic and Muslim girls from across Glasgow whose families want single-sex education.
Its champions say it boosts confidence among pupils particularly in maths and science.
Many parents want the school’s single-sex status to remain.
But some local parents say their choice to send boys to a school in their own community is being denied.
Jill Grady is from campaign group Notre Dame High For All.
She said: "We are delighted that Glasgow City Council have agreed to hold a consultation into whether Notre Dame High School should be co-educational.
"We have campaigned for the right for the people of Glasgow to debate the question of whether Scotland's last remaining state run school should be open to both local boys as well as girls.
"Today's decision opens the door for thousands of people across the city to make their views known and shape the future of the school and we thank Glasgow City Council for recognising that.
"It is well known that the transition from primary school to secondary school is a critical time for children and it is our firm belief that Notre Dame High School should be open to both boys and girls, that boys and girls from Notre Dame Primary School should be able to transition to high school at that vulnerable age together and that the school should first and foremost serve the community in which is it played a key role for many years.
"We would encourage as many people as possible to share their views once the consultation opens on 18 March 2018."
The consultation will look at three options: keeping the status quo; making the school co-educational or keeping it girls-only but adding more local primary schools to its catchment area.
In a report to the committee, Chris Cunningham, the council's education spokesman, said: "Over a long period of time parents from across the city are choosing or have chosen single-sex education in Notre Dame High.
"Retaining this option would benefit families for whom this is a preference.
"Moving to co-education would support families who wish siblings to attend the same secondary school within their community."
A NDHS parent council statement read: “While we also welcome the consultation, we really hope that it will finally give a voice to those families who are directly affected.
“The impact of changing the status of the school goes way beyond the affluent west end.
“Local primary schools are already exceptionally well served by the top performing co-ed secondary schools in Glasgow, right on the doorstep.
“Notre Dame High School is almost full with a majority of families from diverse cultures and backgrounds actively choosing to send their girls there via placing requests.
“Removing that choice, will remove improved opportunity for those areas of our city who do not have top schools close by.
“The school should be held up as an exemplar in our community, in the same way JordanHill, or the Gaelic School are.
“Like them, it offers Glasgow families additional choice, high academic performance and helps close the attainment gap.
"This wonderful public school, the last of its kind in Scotland, encourages, supports and develops young women to reach their full potential and has done so very successfully for over 120 years.
“On the eve of International Women's Day, we would urge everyone to please consider that as apart of their comments on the consultation."
The consultation will go live on March 18.