'How do you get around to listening to 34 pupils reading?'
Even basic, but essential, tasks like listening to each child's reading is a challenge in large classes, explains Gerry Brown, principal of St Mary's senior national school, Blessington, Co Wicklow.
"How do you get around 33 or 34 children along with everything else in the school day?" he asked.
Enrolments in St Mary's are growing steadily, in line with the development of the west Wicklow town, where the population has more than trebled in 20 years.
The two fourth classes in the school have 34 and 32 pupils respectively, about 10 more than each of the other classes in St Mary's.
The improvement in the pupil-teacher ratio coming in September won't bring any benefit to the school this year, although it should be entitled to an extra teacher in 2017.
Mr Brown says the curriculum is supposed to be child-centred but points to the difficulties for a teacher with more than 30 pupils in delivering on that, such as "organising simple science experiments and ensuring that each individual is getting out of the lesson what they should be getting out of them and that the pupils who need the extra bit of help are catered for".
The principal also points to the challenges in maximising the benefits of homework.
"Sure, you can get all the copies corrected, but there is the issue of giving feedback to individuals," he said.