Date Uploaded: 29/03/2016
And it also warns that the current absence of planning could leave schools facing the opposite risk - too many teachers.
An oversupply of teachers is damaging because it results in graduate unemployment and knock-on consequences for attracting talented school-leavers to the profession.
A looming crisis in teacher supply, at both primary and post-primary levels, is spelled out in a confidential report seen by the Irish Independent.
It admits that the issues involved are complex, but warns "the teaching and learning needs of Irish students require that significant priority should now be given to these matters".
The expert group that prepared 'Striking The Balance' for the Teaching Council says work must start immediately on addressing the issues.
The recently-completed report was sought by former Education Minister Ruairi Quinn, and now it is up to the Teaching Council to deliver advice on the steps that need to be taken to deal with current difficulties, and avoid a worsening situation.
Primary schools all over the country are already suffering a shortage of substitute teachers - even to replace staff who are on predictable and long-term absences such as maternity leave.
According to the report, there are only enough substitutes available to work for 64pc of the days that schools require cover - with acute difficulties in some counties.
Meanwhile, post-primary schools are having problems recruiting teachers in a number of key subjects.
There is a lack of teachers of European languages, home economics and Irish and, at the same time, many more than are required for English, history and geography.
Getting the balance right depends on the one hand on pupil numbers, class sizes and, in the case of post-primary schools, catering for different subjects - and, on the other, managing the supply of teachers.
Fluctuations in population are a factor and the emerging challenges come at time when high birth rates since the end of the 1990s have resulted in an explosion in pupil numbers.
Between 2014 and 2018, primary school enrolments are expected to rise by about 30,000 to 574,000, while, by 2025, post-primary schools will have more than 400,000 pupils, for the first time in the history of the State.
A properly functioning system also needs to take account of additional teachers to cover absences, such as illness or career breaks, as well as retirements.
Based on current enrolment predictions and class sizes, the report estimates that there should be enough newly-qualified primary teachers over the next five years to meet needs.
However, any further reduction in primary class sizes - to which political parties have committed themselves, to varying degrees - would throw the sums out.
On the supply side, the report highlights the lack of co-ordination and consistency around intake into teacher training courses, and says it is time that process was properly regulated.
At the moment, the Department of Education controls numbers entering traditional primary teacher training colleges; the universities decide on intake into courses for post-primary teachers; and the private provider, Hibernia College, which trains in teachers for both levels, sets its own intake.
The report states that "greater policy co-ordination and consistency is essential if we are maintain the quality and standing of the teaching profession that we currently enjoy"
The Irish National Teachers' Organisation (INTO) said ensuring teacher supply was an immediate challenge for the next government.
INTO general secretary Sheila Nunan said: "The next minister must make sure that enough teachers are trained to meet commitments for smaller classes."
In relation to problems over substitute teachers, she said: "The lack of cover for teacher absences can only be tackled by establishing supply panels of teachers available for substitute cover throughout the country."
Ms Nunan also said starting salaries in Ireland needed to be increased, to ensure that Irish teachers remained at home and did not go abroad to fill vacancies.
Reversing the austerity-era cuts inflicted on salaries and promotional opportunities - particularly for newly qualified teachers - and schools will be a dominant theme at the Irish National Teachers' Organisation (INTO) conference, as well as at the other two conferences.
Primary class size is a hardy annual for the INTO, and the union will be reminding political negotiators engaged in trying to form a government about their pre-election promises in this regard.
The ASTI is gearing for a double dose of strikes, threatening to close schools in the autumn. Stoppages are planned as part of ASTI's ongoing resistance to Junior Cert reform, although the TUI has signed up to it. But the ASTI and TUI are at one - if at odds with the overwhelming majority of public service unions - in rejecting the Lansdowne Road pay agreement, which could also see strikes in September.
With members at both second level and institutes of technology, much of the conference will be concerned with third-level issues, including the impact of funding cuts.
Plans for forced mergers of institutes of technology as a prerequisite for creating technological universities also very much on their agenda.
Journalist: Katherine Donnelly