The principal of a Carlow Educate Together school says Ireland is 'haemorrhaging' teachers to other countries, after making the profession less attractive.
Simon Lewis, who also presents the 'If I were the Minister for Education' podcast, says he 'felt somewhat sorry' for Education Minister Norma Foley during a recent Newstalk interview.
He was responding after Minister Foley said measures have been put in place to ensure schools always have access to substitute teachers.
Minister Foley said substitution panels have been extended to help plug gaps.
But Mr Lewis told The Hard Shoulder this has not happened.
"The short answer to your question is 'no' - it couldn't possibly happen because there were no other places to look.
"I felt somewhat sorry for the Minister while I was listening to her floundering on your show, to be honest with you.
"She clearly hadn't been advised properly when she came on with you.
"And it seems to be a trend with Minsters for Education for the last number of years: that once you scratch below the surface, they don't have any answers."
But he says a crisis abound substitute teachers is not a new issue.
"I think it's been going on since at least 2014, it's reached crisis levels in 2016, it was only admitted in the Dáil in 2018 by Richard Bruton.
"But nothing has been done to solve the problem.
"We're haemorrhaging qualified teachers out to country's in the Middle East - we've made teaching a less attractive position than it was maybe when I started.
"This is the chickens coming home to roost - unfortunately - and we're no closer, even after your interview, to a solution".
And he says in his school, which educates over 400 pupils, there has not been one day of term where he has had a full cohort of staff.
"I'm in a cluster for this substitute panel, I'm one school out of 18 with three substitutes on that panel.
"My school has a need for at least one of those every day, and I'm not the only big school on that panel.
"The maths is clear: there just aren't enough substitutes around.
"So you're forced to use whatever you can - whether that's a student on his teaching practice or her teaching practice, whether it's a local person who has Garda vetting and a degree behind them.
"You do what you can because the last, last resort - after exhausting your set team - is to send children home".
