The John Flynn Community Group say they have fresh evidence the suburb's school should be heritage protected after an architects group recognised its significance.
But lawyers for the ACT Heritage Council have told the Supreme Court the listing is irrelevant to an appeal currently before Justice John Burns.
The community activists have appealed against an ACT Civil and Administrative Tribunal ruling knocking back their bid for heritage listing.
In court yesterday the group's barrister, Robert Clynes, told the judge the tribunal may have erred when considering the definition of ''community''.
And the group has also said subsequent recognition from the Australian Institute of Architects list of significant 20th century architecture strengthened their case. But the judge questioned whether, in considering the appeal, he could take into account evidence never put before the tribunal.
A stoush over the fate of the school has raged for years.
Designed by renowned architect Enrico Taglietti, the school opened in the 1970s but was shut down in 2006 as part of the ACT Government's city-wide school closures.
The group has argued the school, which has links to John Flynn and the Royal Flying Doctor Service he founded, has architectural and cultural significance to the community.
''This is not just any school, it's a special school, in special circumstances,'' Mr Clynes said yesterday.
The barrister told the court the tribunal erred in finding the word ''community'' under the relevant law did not apply to the group or the suburb of Flynn.
Outside the courtroom, the John Flynn Community Group's Roger Nicoll said it was important the school was recognised not just for its aesthetic value ''but for the value that the community has placed on it over the years''.
The hearing before Justice Burns continues today, and he has reserved his decision on the question of new evidence.