At least five practices, including TP Bennett, Penoyre and Prasad and BDP, worked up schemes to replace the Modern building before the project stalled in November.
Another suggests moving the school to a different site and selling the land, while only the third follows the competition brief and suggests rebuilding the school on the same plot.
Jonathan Darke, TP Bennett principal, said things had become confused. 'There were local [council] elections which saw a change of leadership, and all projects were put on hold. We thought: that's the end of that.
'The Ashmount School competition was a very exciting project, and we had come up with some innovative designs.
'Half a dozen or more councillors involved at the beginning of the competition wanted to see the project go through and the wheels are beginning to get back in motion now.
'The councillors realise they cannot avoid this problem. Ashmount School has concrete cancer and is in a state of disrepair; the project is once again gathering momentum,' he added.
But the competition now faces fresh opposition: the conservation lobby has woken up to the possible demolition.
James Dunnett, of preservation group Docomomo, said: 'Ashmount School would present a major challenge for any architect seeking to bring it up to modern standards of insulation while retaining the value of the original design, but Docomomo believes the quality of the architecture makes a thorough study of the possibilities an essential step.
'We urge Islington Council to commission such a study before taking any decision, and to reject the idea of re-building the school on Metropolitan Open Land - greenery of which Islington is desperately short,' Dunnett added.