Victoria Greenaway works as a full-time temporary science teacher at a public high school in south-west Sydney. She has been waiting for a permanent teaching position since she graduated from university seven years ago, when she did not anticipate the uncertainty of teaching. ''It affects my career in that certain promotional positions are not available to me because they've got to know that you're going to put your time in at that school and they don't know if they're going to be able to employ me next year,'' she said. ''It affects your sense of belonging in the school community … and when it comes to things like mortgages, can I commit to buying a flat?'' The NSW Teachers Federation says the fight for permanent roles is being worsened by an increasing preference for casual workers. ''We have thousands of positions that should be filled permanently currently being filled by predominantly young teachers on a casual or temporary basis,'' the federation's president Maurie Mulheron said.

He said some young teachers were giving up on the profession because they were frustrated that only casual work was being offered. A spokesman for the department said it conducted regular reviews of casual and temporary teacher usage in schools across the state. Each year, about 2200 new permanent teachers are appointed to public schools. But last year, there were about 6353 teaching graduates, up from 4669 in 2003, according to department estimates. Because of the oversupply, most graduates start their career as casual or temporary teachers and some wait years for a permanent job. The union plans to prosecute the department over what it says is a deliberate attempt by ''a small minority of principals'' to leave permanent positions unfilled ''as a way of intimidating young people''.

One casual teacher in the Hawkesbury area, who did not want to give her name because she is applying for jobs, works across five public and Catholic primary schools and often does not know if she is working until 30 minutes before she is needed. The 24-year-old, who graduated last year, has a permanently packed suitcase containing work to teach every year group. ''You can never plan anything and I'm a very organised person, so that's stressful,'' she said. ''I'm trying to save to get a unit but I can't even make a budget because I don't know what [work] I'll be getting.'' She said she would have considered a different career path if she knew how difficult it would be. The department spokesman said there was no time frame for how long teachers were on the waiting list.

''Factors that influence when a teacher is appointed to a vacancy include the school's curriculum needs, the teacher's accreditation and areas of expertise, the geographic locations in which he or she is prepared to work and his or her priority date for employment.'' But while the pool of primary teachers is high, there is a growing need for those teaching high school subjects such as maths and some science and technology subjects. Between 2006 and 2012, creative arts had more than twice the number of graduates as mathematics. The vice-chancellor of the Australian Catholic University, Greg Craven says it is a supply problem. ''It's not that universities don't want to teach science and maths teachers,'' he said. ''It's just they're not presenting.''