Teachers' strikes across NSW on Wednesday are due to failures by the NSW Premier Dominic Perrottet and Education Minister Sarah Mitchell, NSW Teachers Federation Deputy President Henry Rajendra says.
"The Premier has ignored the calls of the profession to address teacher shortages across the state," he said.
"In early October there was a meeting between the Teachers Federation and Department - the secretary or minister was not there.
"We invited the Premier to sit down with the union last term to address this issue and he failed to do so.
"Having failed to address this, having failed to listen to the profession, the strike will proceed."
Read more: Catholic teachers back NSW school strike
Teachers want increased salaries and staffing to make workloads more manageable and attract more people to the profession.
There are more than 100 permanent teacher vacancies across the Illawarra.
Former principal Vicki Walsh said it is also increasingly difficult to find casual teachers to cover for sick and parental leave.
"Best practice looks like having someone well-trained, well-supported and specialised in that area in front of a class every day, with enough casuals available to cover people off with COVID, people getting married, people having babies," she said.
"Teachers are people, life happens."
Ms Walsh said the amount of administration teachers are required to do has become impossible to manage.
The more children with additional needs in a class, the more time their teacher must spend justifying the support they receive.
"The amount of compliance, training and documentation teachers have to submit is crazy," she said.
"Teachers are required to document every adjustment they make to a childs' learning to justify any additional support, for ten weeks, for every student, every year.
"This is to make sure they don't ask for more than they need.
"What would be the point of a teacher asking for more support for a child than they needed?
"The only people that support can help are the children in the classroom."
Sign up for our newsletter to stay up to date.