If I could change one thing in education I'd probably spend a week agonising over the choice. I'd love to insist that the Department of Education and Skills would end, once and for all, the presumption that a person's constitutional right to an education ends at age 18. I know it's based on a Supreme Court judgement but it's stupid and cruel, and applied in the most arbitrary way possible. That is especially so for people with an intellectual disability, for whom their 18th birthday often becomes the moment they're cut off from services they desperately need.

Or I’d love to reorganise the special-needs assistant system from scratch, making them a school-based service and giving them proper career structures.

Or I’d force the entire school system to start displaying a bit of common sense, and exercising parental choice, over such things as expensive crested school uniforms.

But if there was one thing I could do in education, and only one, I'd make the one change that would build a lasting legacy for future Irish children. I'd probably have to be taoiseach to do it, because I would want to commit Ireland to building the best possible preschool system in the world. And I'd want to give every Irish child the right to enter that preschool system once they get to the age of three.

It requires an investment we’ve never been willing to make. Up to recent years, the annual OECD study on investment in education showed, year after year, that as a proportion of our national wealth, Ireland invested a little more than the OECD average in third-level education, about the average in second level and a bit less than the average in primary. And nothing at all in preschool. For years, that column was left blank.

Now, after the introduction of the free preschool year, we spend 0.4 per cent on preschool education. That's around half the average spend across the OECD. Some countries, of which New Zealand and the Scandinavian countries would be leading examples, spend a lot more.

A free preschool year is not a system. We have introduced a free preschool year with no curriculum, no framework of standards, loose regulation, and little in the way of staff training or career development. We give grants to thousands, literally thousands, of providers, enable them to hire staff at the minimum wage, and tell them to get on with it. Some have managed brilliantly. In other cases, we have done little more than lower the cost of childcare. And then there are the cases that featured on Prime Time not so long ago.

We need to invest in two things. First, we have to develop the quality of what we have. While some of the building blocks are in place, we don’t really have a system in which parents can believe, or that will really help their children to grow and flourish.

The mantra “no care without education, no education without care” is truer when a child is very young than at any other stage in the child’s life.

When we’ve got the quality right, we need to extend the system. Most children start school in Ireland between four and a half and six years of age. If they had access to two years of high-quality preschool before they go into “big school”, it would be hugely advantageous to them.

We talk endlessly about breaking cycles. Nothing breaks the cycle of disadvantage, poverty, alienation, debt, dependency, marginalisation, early school-leaving, crime, gang membership and inequality the way education can.

Giving every child the chance of the best possible start, through a preschool system that is centred on their need to develop and grow and to be happy and safe, would be the best possible investment we could make in the future of our country.

Fergus Finlay is chief executive of Barnardos children's charity