The results, which arrive in August, determine which university they can get into and what course they can do, or what kind of job they can get if they decide not to go to college (presuming they can find a job, of course).
So how a youngster does in the Leaving Cert opens doors into the future -- or slams them shut. It's probably the most important exam they will do in their lives. The pressure to do well is enormous.
Competition for university places is always intense here, and it's worse than ever this year because of the depth of the Irish recession. With no jobs around even more kids are trying to get into college. What this means is that to get into even ordinary degree courses in, say, arts or business, a youngster has to get very high points.
The reason the points are so high is that we don't have enough college places for all those who want to get in, especially in particular degree courses. The more kids want to get in to a particular course in a particular university in a particular year, the higher the entry points for it will be that year. It's all worked out by the computers in the state run Central Applications Office every year.
Points for university are allotted on the basis of performance in the Leaving Cert exam. The way the system works is that the marks in a student's six best subjects in the Leaving Cert are converted into points and then added up to give an overall score.
A perfect score is 600 points (100 in each subject). To get this you need to have between 95% and 100% in each subject. Many students do seven subjects as a kind of insurance against something going wrong in one subject. But only the results from the six best subjects are counted.
To get into any of the professional degree courses, like medicine, dentistry, psychology, law and so on, you need to get around 90% in all subjects. To get into even run of the mill courses in a main university here, say a general arts degree in English and history or a basic business degree, you need to get nearly 70% in all subjects in the Leaving Cert. And we are talking here about subjects at higher (or honors) level, not ordinary level.
To achieve this level of perfection in one or two subjects is tough. To get it across all your subjects is incredibly difficult and can only be done by hours of after-school study and cramming and weekends spent in grind schools.
And that is what so many Irish kids do, turning their last two years in school, when they are 16-18 years old, into a nightmare marathon. The nightmare of the points race.
Welcome to the Irish education system. It's an absolute disgrace, a system which suits the Department of Education here and the teachers, but turns the lives of too many of our young people into a living hell.
Many kids cope, of course, and a small number even thrive on it. But for a great many it engenders feelings of inadequacy and hopelessness -- to the point where there have even been suicides.
We did away with university fees here about 30 years ago to help poorer kids get into college. It has helped to a limited level, but poor families can't afford to pay for extra tuition for the Leaving Cert, so the poor kids are now at a big disadvantage in trying to meet the required points level for entry.
We introduced the points system to avoid the situation in which kids got in because daddy was a doctor or mummy was a lawyer, and both of them knew someone on the staff in their old college who could get young Sean in even if he was as thick as a plank.
And it has done that, which is good. But the points race that has developed over the years is bad, causing huge distortion and damage in the way we educate our children.
What it means is that a lot of kids now choose Leaving Cert subjects solely on the basis of which ones they think will give them maximum points. An example would be the sciences. We urgently need to get more kids to do engineering in college, for which they should be doing physics or chemistry in the Leaving Cert.
Of the three Leaving Cert science subjects, physics, chemistry and biology, the biggest number of kids who do science take biology. Why? Because it is seen as the easiest one in which to get high points.
It may or may not be relevant to their future careers, but biology is the chosen one. And it's a similar story across other subject groups as well.
There are three core subjects that everyone has to do, Irish, English and maths. A high number of kids do ordinary level Irish as a seventh subject because they hate it and see it as useless in their future lives.
The latest trick among the families who can afford it is to pay a psychologist to say Sean has dyslexia and therefore can't do Irish. These kids (a couple of thousand of them last year) get an exemption from Irish ... but many of them then go on to study French or German!
One of the biggest failings of the Irish high school system is its inertia, its failure to change. You can do classical studies (studying ancient Greece and Rome) or Latin as Leaving Cert subjects.
But you can't do computer science. You don't need a lot of points to know that is stupid.
There are all these teenagers in Ireland (like mine) who know how to do highly complicated downloads, uploads and conversions on their computers and can play all kinds of super-complicated PlayStation games online with people in Japan or South America. But, although there are around 40 possible subjects for the Leaving Cert, computer science is not one of them.
Why? Because we don't have the teachers. And more importantly, we don't have the money to put a computer room into every school.
So the next time you hear an Irish government minister talking about the knowledge economy in Ireland and how good we are at information technology, think about that because that's the reality.
Here's another example of our failure to change -- languages. We start with the huge advantage of being native English speakers.
But Russian or Chinese would be good to study as a second language these days. Or Spanish, which is the second most spoken language in the world today (and of course of growing importance in the U.S.). Or German, since Germany is now propping up the Irish economy as well as the rest of Europe.
So how is this reflected in Irish schools? Last year around 27,500 kids did French in the Leaving Cert, in comparison with 7,500 who did German and 3,000 who did Spanish.
Now I know that Monsieur Sarkozy and his amies think that Paris is the center of civilization, Europe and possibly the world, but the reality is that France doesn't really matter that much any more.
So why are nine times more Irish kids studying French than Spanish, a real world language? Because that's what all the teachers learned when they were in school, it's self-perpetuating and our government is too inept to change it.
Overall, the Leaving Cert course is too literary and too out of date. Most of what the kids have to study is irrelevant to them.
A major weakness is that instead of developing critical thinking and problem solving ability, it involves the rote learning of vast amounts of information which can then be regurgitated in the exam to get maximum points.
All these factors combine in the major problem we now have with maths. So few kids here do higher level maths in the Leaving Cert that the department is now considering giving bonus points for it.
The kids avoid it because they can get the points more easily from other subjects. In this year's Leaving Cert, for example, around 8,000 kids did maths at the Higher Level but around 46,000 did it either at ordinary or foundation level (very basic). This compares with English, for example, with 33,000 doing higher level and 18,000 doing ordinary level.
The maths problem is so bad that it prompted senior executives of U.S. companies here (including Google, Intel and Hewlett-Packard) to have a meeting with the Irish education minister last December in Google's Dublin offices to tell him how worried they are about it.
The Irish graduates they are getting just don't have the think-on-your-feet, problem solving ability they need. It's because students carry on their maths-related aversion into college and avoid degrees in science, engineering and computers.
And it's a problem with its roots in the points race and our Dickensian Leaving Cert system. Our kids know all about Shakespeare but not enough about complex numbers. It's got to change.