A lifting of the restriction on the use of retired teachers in classrooms is under consideration in response to growing shortages of qualified staff for key subjects in second-level schools.
It is one of a number of measures now being examined by the Department of Education as a short-term answer to a worsening crisis over teacher supply.
Education Minister Richard Bruton said it was also looking at the possibility of allowing teacher trainees, in the second year of their post-graduate study, to fill gaps.
Another idea the department would explore is conversion courses to upskill existing teachers to teach other subjects, he said.
Mr Bruton said there is "no quick fix, but there are a number of short-term measures we can take".
In the longer-term, a report on teacher supply from the Teaching Council has put forward models for addressing the issue in a structured way, he said.
The scale of the problem was outlined in stark detail to Mr Bruton yesterday at the annual conference of the Association of Community and Comprehensive Schools (ACCS).
ACCS president Antoinette Nic Gearailt revealed findings of a recent survey in which 96pc of its schools reported difficulties in recruiting for regular part-time or temporary full-time contracts.
She said recruitment goes on throughout the year, such as providing cover for maternity leave, career breaks and professional development, while trying to fill "short-term unexpected absences has become a nightmare".
The biggest problem is with Irish, where 67pc of schools reported difficulties, followed by modern languages (51pc), maths (30pc), home economics (26pc), science - mainly chemistry and physics - (20pc) and special needs (14pc).
She gave an example of one school that advertised three maternity positions, but received no applications, while another filled a position after advertising eight times.
"And the story is the same across most schools. In effect, school students are not being taught by qualified teachers," she said.
Ms Nic Gearailt said there was a need for both short-term and long-term solutions as "schools cannot limp along as they are at present, not knowing if they are going to have teachers".
The ACCS president suggested options such as conversion courses for existing teachers and a reconsideration of the position of post-graduate students, in the second year of the course, who spend a lot of time on the school premises but not in a teaching capacity.
Mr Bruton has a Teaching Council report on teacher supply on his desk, which, he said, he would be publishing in the second quarter of this year and which, while "very valuable but does not offer an instantaneous solution".