The length of the school day in primary school is 5 hours and 40 minutes. This includes assembly time, roll-call and breaks which are usually around 11am and 12.30pm. Primary schools may reduce the school day by an hour for children in their first 2 years at primary school (commonly called junior infants and senior infants) and in their third year at primary school (commonly called first class). You can read the Department of Education and Skills (DES) Circular 11/95 Time in School (Primary) (pdf).
Overall, primary schools must be open for a minimum of 183 days in each school year. All schools must close for the months of July and August. Christmas, Easter and mid-term breaks are standardised in both primary and post-primary schools.