Teaching matters: Some time ago in a bookshop, I overheard a very young woman with an accent like Ross O'Carroll-Kelly's younger sister. She was complaining loudly to another young woman working there about their boss, who had obviously just corrected her for something. "

So I said to him: 'It's not like I give a damn. I'm only here for my drinking money.'" You could feel the collective wince from the adult customers in the shop.

Sadly, it is a phenomenon that every teacher recognises. In more affluent schools, pupils work to subsidise their highly active social lives. In less well-off areas, young people work more from necessity, and often work longer hours.

At times, it can seem as if school is a sideline to the part-time work, and not the other way round. The wealthier students give up as the exams approach, but others have less choice. Once again, those who are already well off have a built-in advantage, because the young person who continues to work long hours cannot possibly sustain a full workload of study at the same time.

McDonald's recently announced that it will no longer allow Leaving Cert students to work for it during the school week. It will alow them to work only at weekends and outside term time. Now if only all the bars, petrol stations, shops and other fast-food outlets that employ second-level students would follow suit ...

Selina McCoy and Emer Smyth of the ESRI recently published some research on this area. "At work in school - part-time employment among second-level students" makes for very interesting reading. Some 60 per cent of Leaving Cert students work. If you are male, you are much more likely to work longer hours.

There is some correlation between working long hours and early school leaving, especially at Junior Cert level. The authors point out, however, that there may be an element of self-selection at work here.

Students who are already poorly motivated and somewhat disengaged may choose to work longer hours as a means of getting out of school faster. Of course, a job that appears a way out of the boredom of school may appear very different a few years down the line, when the young person realises that a lack of qualifications has severely limited the options open to him/her.

It is not only paid work that takes up time. Young people also do a substantial amount of unpaid work. This might seem obvious in young people from a farming background, but urban young people can also work without regular pay, for example, in the family business. Some 12 per cent of students work in this way. I wonder how many young people are involved in demanding caring work? Every teacher knows of family situations where an older child virtually has the care of a much younger sibling, or where parental disability means that a young person runs the household.

Babysitting seems the most innocuous option, and girls who babysit get substantial amounts of homework done. However, I think we are much too complacent about girls, and it is almost entirely girls, in their early teens, taking responsibility for very young children. The Irish Red Cross launched a very useful booklet on this topic last year, "A Handbook for Babysitters and Parents". Some of the research is very revealing. While parents had very few worries about leaving their children with teenagers, the teenagers themselves expressed significant anxiety. What if a baby chokes? Or starts running a really high temperature? This is a massive responsibility for relatively young people.

Some parents do not even leave contact numbers, even in this age of the mobile phone. Some young people are scared of incidental noises, or the normal sounds of a household. The Irish Red Cross points out that such nervousness could impede judgment in other areas. Also, some young people are intimidated by alarm systems, and even managed to get themselves locked out.

The casual attitude of some parents is hard to believe. One of the worst incidents reported was when a babysitter found another child asleep in the house an hour after the parents had left, a child who had never even been mentioned. In another incident, the couple returned to the house and began to fight and throw dishes.

Part-time work does have some positive aspects. Teenagers enjoy being treated like responsible adults, and usually they rise to the challenge. It is a valuable learning experience to have to be on time, to follow instructions and take the initiative where appropriate.

It can help young people to grow up. However, given that the vast majority of young people work in unchallenging service work, it is questionable how much their skills really develop. Further, if like our young friend in the bookshop, the work is primarily to fund alcohol consumption, that raises questions, too.

I also wonder how many young people who lose out on study time end up taking expensive grinds? That is an issue that might be the subject of further research. Perhaps the solution lies in integrating substantial amounts of work experience into the curriculum, and in greater enforcement of the regulations concerning young people and work. It would be a pity to be too draconian, however. After all, part-time work for many young people marks an important rite of passage in that difficult transition from childhood to adulthood.

• Breda O'Brien teaches at Muckross Park College, Donnybrook, Dublin, and is a columnist with The Irish Times.