The capital is already home to almost half of the educational organisation's 65 primary schools.
However, Educate Together does not currently manage a single secondary school within the city catchment area.
Olivia Morahan, one of the campaigners from five Educate Together primary schools, told the Herald: "We want this school because of the whole ethos, it's child-centred and it's democratically run and multi-denominational.
"From my own experience, I've two children in the early years of an Educate Together primary school and it's a very different schooling to what I experienced growing up.
"There are demands on both sides of the city, so in the long term the best solution would be one for the northside and one for the south," said Ms Morahan, who has Emma (8) and Amelie (6) in an Educate Together primary.
The group says there is demand for two schools, but they are initially looking for one.
"The idea is for co-patronage of an existing school rather than a new build," a campaign spokesperson said.
Campaigners said they are trying to pressure Education Minister Ruairi Quinn to set a timeline for when they can expect to see an Educate Together secondary school in Dublin.
The increase in demand for an Educate Together secondary school in Dublin is said to be driven by the number of children coming through the primary level equivalents.
A meeting will be held in Wynn's Hotel in Dublin city centre to progress the campaign tomorrow night.
Educate Together spokesman John Holohan said no decisions have been taken yet on where the proposed school would be. "There's no location suggested yet, but Dublin is where the need is," he told the Herald.
"The challenge in areas like the city is securing the schools outside the existing system.
"We will be supporting the parents in Dublin to try to get a school there."