NSW faces a shortage of teachers and risks running out of school staff in the next five years, internal education department documents reveal.
The confidential audit last year found plummeting graduate teacher numbers, rising enrolments, and an ageing workforce are just some of the issues the department faces.
"We cannot improve student outcomes without having a sufficient supply of high quality teachers available where and when they are needed," an executive summary from June 2020 concludes.
"If we don't address supply gaps now, we will run out of teachers in the next five years.
"NSW public schools have a high proportion of out-of-field teachers, which impacts student outcomes."
The teachers' union says the government has not heeded the warning.
"These documents show the government has been fully aware of the worsening staffing crisis and has betrayed teachers, parents, principals and students by repeatedly denying the seriousness of the problems instead of addressing them," NSW Teachers Federation president Angelo Gavrielatos said.
Teaching staff shortages were also found by the Independent Education Union which surveyed 377 Catholic schools in February and March.
On average, about 44 per cent of secondary schools and 23 per cent of primary schools surveyed had a temporary or permanent teacher vacancy.
The union - which represents more than 32,000 teachers from non-government schools - said the shortages had only intensified as the year progressed.
"When schools on Sydney's north shore struggle to secure staff, you know you've got a problem," IEUA acting secretary Carol Matthews said.
But the NSW Education Department says the projections are rolling figures involving a number of assumptions and data sources.
It says the information uses only one data point and "is very out of date".
"To retain the most up-to-date projections on teacher supply and demand, the department updates these models and the resulting forecast regularly," an education spokesperson said.
Education Minister Sarah Mitchell said the department's approach to teacher supply was backed by research.
"Claims that we are heading for a teacher crisis are blatantly misleading and self-serving," she said.
"Ensuring we have the best teachers in the right place is not fixed by a fear campaign backed by bad data."
NSW Auditor-General Margaret Crawford in April reported that the state agency responsible for implementing strategic plans for school assets was not prioritising the right projects.
School Infrastructure NSW identified the need to accommodate an additional 180,000 enrolments in public schools by 2039, and upgrades to about 34,000 teaching spaces to be fit-for-purpose.
The audit found the agency was focused on delivering existing projects, election commitments, and other government announcements that diverted attention away from strategies that better met present and future needs.
Shadow education minister Prue Car said the documents revealed the teacher shortage was worse than earlier reported, despite the government saying it was a "beat up".
She said the shortages were particularly bad for maths and science teachers.
"The Liberal government allowed this to happen - and now they're trying to cover their tracks by flying in overseas teachers with no Australian experience," she said.