how to choose a primary school in south Dublin?private school or public school?

People normally choose a primary school that is close to them and aligned with their values/ethos if that's possible. And religion is important for some families. A 'very' catholic school might not be suitable for a non-denominational child. Also, single sex or not? Answer these questions and then look at schools local to you that fit.

Visit the schools you are interested in and see what you think. It is important for kids to go to school local to them as that's key for making friends and been part of the community. Hard to be part of 'walk on wednesdays' when you live far away.

'Free' schools are in theory free but there are costs for uniforms, books, school upkeep/heating contribution, school charity fundraisers etc.

Johnstown (Public) could be worth a shout, based on the areas outlined above.

My own personal opinion - and the rough plan for my 1 year-old son - is public for primary and private for secondary. I was public/public and my partner private/private, so we have at least a passing idea of each.

I don't think private primary offers anything (much) greater that would justify the increased costs. I dislike the existence of private schools, but still intend to send my son there for secondary education as the reality is that, on balance, private 2nd level is likely to position him better for what follows.