Some 65,000 Leaving and Junior Cert students will take private grinds this year, with grind schools already reporting large attendances at their Christmas revision courses.
Such courses, however, were criticised by teacher unions yesterday.
Thousands of students who are preparing for their "mock" exams have been attending five-day crash courses costing up to €550 over the Christmas and New Year period.
Reflecting the financial demands on parents before the State exams,the Institute of Education in Dublin charged €535 for five Leaving Cert subjects, while the Limerick Tutorial Centre and Bruce College,Cork, offered five subjects at €390.
At the lower end of the price scale, Cork Leaving Certificate College offered five subjects for the price of three subjects at €250. Such is the popularity of grind schools that the grind "industry" is estimated to be generating €50 million annually.
However, holiday revision courses have been criticised by teachers' representative bodies.
Paddy Healy, president of the Teachers' Union of Ireland, said the Christmas break should be a time of relaxation for students before they begin the final terms of intense study.
"These crash courses are a byproduct of the annual points race and the accompanying fear of losing out and are, of course, operated for financial profit.
"Also, it is not expected that the subject curriculum would be complete by this stage, while very often these courses operate on the basis that everything has been studied by the student."
Association of Secondary Teachers Ireland president John White said there was "no magic bullet" to ensuring success in exams, and only in circumstances where a student has been absent from school due to illness could intense grinds be justified.
"There is simply no substitute for steady, regular and consistent work. Any institution or so-called grind school that creates the impression that they can provide a magic solution to ensure success is misleading students."
However, Dr John O'Halloran, principal of the Limerick Tutorial Centre, said 464 Leaving Cert students were attending their revision courses this week, and it would aid their preparation for the "mock" examinations.
The number of enrolments in Cork Leaving Certificate College increased by 5 per cent this year, with the number expected to double, if not treble, for the Easter revision courses, according to its principal Maura Ryan.