The campaign for an inner-city high school began, like many calls to action, at a dinner party.

Three years ago a few young couples were catching up over a glass of wine at a Surry Hills terrace that overlooks the academically selective Sydney Boys and Sydney Girls high schools.

''Those schools were so close to where we all lived, yet they were completely out of reach for our kids,'' Skye Molyneux said. ''We were just thinking, 'Gosh, our kids have had this great primary school experience and they are really close friends but when it comes to high school they'll get scattered across the city'.

''We were all such supporters of public education but it struck us that we were all choosing private schools, not because we believed in them but because it was actually the only option.''

The campaign that was born from that night's table talk has had its first significant victory. The Inner City Schools Working Party, having solved the primary school capacity problem in Ultimo with a new 1000-student school, has turned its attention to the need for a high school.

''It's a huge step for our little campaign,'' said Ms Molyneux, a founding member of the Community for Local Options for Secondary Education (CLOSE). ''Up until a couple of weeks ago it really felt like we were talking to a brick wall. But the people on the working party are well aware that there is a capacity issue and they've got to do something about it.''

Enrolments at the local primary schools - Bourke Street, Crown Street, Darlinghurst and Plunkett Street - have swelled in recent years. Bourke Street had 74 students in 2010 and the Department of Education forecast then that it would have 112 this year. Yet when school resumed last month, 230 students showed up.

The City of Sydney's demographic forecasts predict the school-aged population will grow by more than 7000 between 2006 and 2021. The Department of Education estimates 70 per cent of the city's students attend public schools.

Most students in the inner city are zoned for comprehensive high schools in Balmain, Rose Bay and Alexandria. But those schools have reached capacity or are difficult to reach by public transport.

When the working party meets for the first time next month, everything will be on the table.

A department spokesman said ideas would be gathered from interested stakeholders, ''most importantly parents''.

A school site on Cleveland Street, used as an intensive English centre, has been touted by campaigners as a desirable option. The department has repeatedly said it has no intention of moving the program or incorporating a local high school stream.

Opening places at Sydney Boys and Sydney Girls for non-selective local students has also been suggested, to the objection of many current and former students.

The option favoured by most is a new, purpose-built high school that could be incorporated into the Central-to-Eveleigh redevelopment.

That is the preference of Sydney independent MP Alex Greenwich, who says a vertical high school should be considered, ''particularly if it is close to a park''.

''We need to acknowledge the reality that we do live in the inner city, space is limited and we will have to look for a creative solution,'' he said.