Almost half of 614 Leaving Certificate students in a new survey reported working during school term, with boys doing an average of 20 hours a week and girls an average of 16 hours.
The study, conducted by the Irish Congress of Trade Unions, showed that 49 per cent were working in the retail sector, the most popular choice for jobs. Other popular areas were bar work, restaurants, farming and construction.
The majority of the students said they were working to earn money for "socialising and hobbies". However, the jobs they were working in paid an average hourly rate of £3.47, which is considerably below the new minimum wage of £4.40 per hour.
There was little change in the numbers working between 5th and 6th year, the study disclosed. The highest percentage of students in employment was among those on the Leaving Certificate Vocational programme, while the lowest was among those repeating their Leaving Certificate.
Most of the work took place at weekends, according to the study and the majority of the students said working had no effect on their school activities.
"It was their opinion that they were not working enough hours during the school week that it would interfere with their academic life, that they could manage their time effectively," the study said.
Those who decided not to work said they wanted to concentrate on their Leaving Certificate. These respondents said they were "under enough pressure as it is", according to the summary of the survey. One-third of students said they gave some of the money earned to their parents, while more than half (54 per cent) said they used some of it on school expenses. Only a minority received pocket money while they were working. Those who did received slightly less than £13 per week.