Any single set of test results in an international survey has to be treated with caution. Outcomes can fluctuate unexpectedly up and down. But this very positive outcome tallies with other information that we have about the reading achievement of Irish pupils.

The National Assessments of English Reading and Mathematics, published in 2014, showed the first significant improvements in the reading achievement of Irish primary pupils for over 30 years. Data from the Educational Research Centre's evaluation of the DEIS initiative in schools serving pupils from disadvantaged backgrounds have shown consistent improvements in pupils' achievement in reading and maths.

So what has brought about this welcome improvement in literacy? There is no single cause for the gains we see. Instead, I think it is fair to say that a combination of factors and a coordinated effort across many fronts have helped bring about improvement. Certainly, yesterday's results are a tribute to our school leaders and teachers who have worked assiduously to raise reading standards. PIRLS data shows, too, that Irish parents are deeply committed to providing the home atmosphere that supports their children's learning.

Probably the most significant initiative to support schools and parents in this work was the National Literacy and Numeracy Strategy 2011-2020, the first fully coordinated national attempt to set out clear targets and a range of linked actions to improve literacy and mathematics in schools. It has supported and challenged the education system in a range of ways to improve reading (and mathematics) achievement. The 4th class pupils who took the PIRLS 2016 test experienced the changes the strategy brought about since they were in infant classes.

Schools were asked to increase the time available for the teaching of the core skills of literacy. Teachers were also encouraged to extend the teaching of literacy throughout all areas of learning in a broad and balanced primary school curriculum.

School Self-Evaluation (SSE) was introduced in 2012. SSE asked principals and teachers to examine how well their own pupils were learning and to identify how their achievement might be improved. A range of supports was provided and schools were encouraged to set targets and monitor how well they were improving learning. School inspections were altered to bring a sharper focus on literacy and numeracy achievement.

Standardised tests of reading became mandatory at 2nd, 4th and 6th class levels and schools have to share the results with parents. In addition, schools were required to look at the overall trends in their data and report to the Department. This helped to create a culture where monitoring and improving outcomes is becoming a routine part of school life.

Initial teacher education programmes were revised significantly to enhance young teachers' capacity to teach literacy. A major investment was also made in the Professional Development Service for Teachers.

So the improvements we are seeing in PIRLS 2016 come after a sustained period of effort and focus on literacy in our primary schools. They demonstrate that when challenging targets are adopted and there is a strategic, system-wide effort to address them, improvements can be achieved in pupils' learning.

The challenge now is to build on this success. Initiatives included in Minister Richard Bruton's Action Plan for Education 2016-2019, such as the Excellence Fund, revised literacy and numeracy targets, and comprehensive policies for STEM education are seeking to bring an equally ambitious and concerted approach to the development of other elements of the school system. It is through such focussed approaches, matched by necessary investment, that the Action Plan's goal of having Ireland become the best education system in Europe by 2026 may be realised.

Harold Hislop, Chief Inspector, Department of Education and Skills