Sydney may be left with just one tertiary art school, with the head of the National Art School conceding the institution may be forced into a merger with the University of NSW.

The school's director Michael Snelling said "it's on the cards" following the announcement last week that University of Sydney's art school will merge with UNSW Art and Design.

But Snelling said he was confident the NSW government recognised the value of the art school as a stand-alone institution.

"We're working really hard to make sure the school retains its distinctive qualities and stays on its site," he said.

Fairfax Media reported last year that the heads of Sydney's tertiary art schools had held discussions for the past year about how to work together.

Snelling said the discussions, which also involve the NSW government, would continue to explore if there was any benefit from combining resources and teaching, and "to see whether there was any legs in the argument to have one or two larger, rather than three smaller [art schools]".

Snelling said it was "not immediately apparent" that merging the NAS with another art school would produce a positive outcome.

"I think diversity is really good," he said. "Choice is a good thing for students to have, especially in an area like all of the creative arts, where what you're trying to do at the teaching end is to produce people with a distinctive and individual voice."

Former NAS director Bernard Ollis said he was dismayed by merger talks, describing the art school housed in the historic Darlinghurst jail as a "national treasure".

"If the state government does not wish to support this unique school on its present site or fund it sufficiently to survive and prosper, then it should seek the support of the federal government ASAP and create it as a NIDA-type institution in order for its needs to be met," he said.

"It is a simple, quick and inexpensive answer to a long and protracted issue."

The school's studio-based style of teaching is beloved by artists and is particularly strong in drawing and painting, but the institution has been repeatedly threatened with closure and merger.

Its alumni include Margaret Olley, John Olsen, Martin Sharp and Ken Done.

The latest threat to the NAS could be the sale of its historic inner-city site after ownership was transferred from the NSW Department of Education to Property NSW.

But any attempt to merge or move the school will be fought, according to Bernadette Mansfield, president of Friends of the National Art School.

"For the state government to seek to homogenise tertiary art education in a city of 5 million people is catastrophic," she said.

"I understand they are looking to London with its University College of the Arts, a similar hybrid of art institutions, and appear to believe that this can be successfully replicated here, with a fraction of the population and with a government that displays little or no intention of supporting the arts."

Mansfield began the NASEXIT petition on the change.org website, which had attracted more than 900 signatures on Tuesday, calling on the NAS to withdraw from merger discussions and for the federal government to take over funding of the institution.

"I will protest against any diluting of the National Art School's proven educational philosophy and will work alongside the other two art schools to ensure our individual campuses are protected," Mansfield said.

"Why would every alumni, from each of the three schools, not stand to protect that which has provided them with so much?"