The Teachers' Union of Ireland has accused the Department of Education and Youth of a continuing failure to address what it has said is a teacher recruitment and retention crisis at post-primary level.
The union said 75 schools have told it they advertised jobs within the past six months for which they received no applicants.
They were among 101 schools that responded to an online questionnaire sent to schools by the union's principals and deputy principals association.
Around 60 schools said they had unfilled vacancies due to recruitment and retention difficulties. Nineteen schools said they had been forced to drop subjects.
Most of the 101 schools said they had experienced teacher recruitment difficulties since September, and more than half said they had experienced teacher retention problems.
The union said students were losing out on a daily basis as a result of the failure to meaningfully address this issue.
The TUI said action was needed from Minister for Education and Youth Hildegarde Naughton and the department to allow schools offer the full breadth of subjects and to ensure that students were taught by qualified teachers.
"It has long been our belief that our policy makers have been happy to 'ride out’ the crisis until student demographics at second level change.
"However, this is an insult to the students currently in the system who are losing out in terms of subject options and inconsistency in terms of the teachers standing in front of them," TUI President Anthony Quinn said.
The TUI has called for access to full-time jobs for new entrants, saying that currently this is the exception rather than the norm.
It wants more career progression options for teachers and a halving of the duration of the two-year PME required to teach at second level.
It has also called for better financial recognition of the experience gained by teachers returning from working abroad, and for a reduction in what the union said is an unsustainable workload that is driving many from the profession.
Subjects are being dropped
TUI president Anthony Quinn said secondary schools are starting to drop certain subjects because of a lack of teachers to teach them.
He said there are particular subjects for which school heads are struggling to find teachers.
"There are some pressure points particularly around the likes of Maths, Irish, Home Economics, Science subjects, but also, worryingly, practical subjects."
Speaking to RTÉ's Drivetime programme, he said these are subjects like construction studies, engineering, technology, which will be "the conveyor belt or feeder into industry that's going to help the country build accommodation and houses going forward".
"And it's hugely remiss of us if we don't build those skills among students, and it's also preventing them from pursuing that as a career choice."
He said an added problem was the housing crisis.
"Agencies are actively recruiting in the Irish market, and young teachers, there's a couple of difficulties they're encountering.
"They don't have access to the full-time contracts on initial emplyment, so they're being enticed by full contracts abroad.
