Katherine Donnelly: Adding up population data is just one part of the equation
Decisions on where to establish new schools are based on a range of data from a variety of sources, including new house builds and child benefit payments in an area.
The Department of Education divides the country into 314 planning areas and uses technology to keep tabs on constantly updated information on population trends that allows officials to predict if and where there will be a demand for new schools.
It is known as a Geographic Information System and the sources include the census, local authorities, the Department of Social Protection as well as the Department of Education's own records on school enrolments
Today's announcement of 42 new schools will, no doubt, bring delight to thousands of families in the areas involved who may have been worrying about where their babies and toddlers would find a desk over the next few years.
But it is only a beginning. The next stage in the process is deciding who should run each school, with patron bodies no doubt ready to line up to vie for the hearts and minds of parents whose voice is crucial when the selection is made. The decision-making is overseen by an independent advisory group, the New Schools Establishment Group.
At primary level, more than 90pc of schools are already under religious control - mainly Catholic - so most, if not all, of the new establishments are expected to be multi-denominational, as has been the case for newly established schools in recent years.
But which patron body? At primary level, the well established Educate Together is now seeing competition from the new breed of community national schools run by local education and training boards.
Depending on the applications made by the patron bodies for the different areas, at both primary and post-primary level, many parents will also have an opportunity to considered whether they want an English-medium or an all-Irish school for their children, such as is offered by An Foras Pátrúnachta.
And when that battle is over, they will be lucky to avoid a campaign for a permanent school building that could go on for years.