Although the vast majority of people in Ireland have at least some knowledge of Irish, only a small minority speak it as a community language (in Gaeltacht areas in the west) or in the more widely dispersed Irish-speaking households in the large English speaking area. Primary schools have had a central role in language revitalisation since the late 19th century, by transmitting a knowledge of the language to each new generation. This paper examines how well primary schools have performed in recent decades. Results of a national comparative study over a 17 year period show that there has been a long-term decline in pupil success in learning Irish (speaking and listening) in ‘ordinary’ schools. Proficiency in Irish in all-Irish immersion schools in English-speaking areas have held up well despite rapid expansion. Reasons for the decline in ordinary schools include time pressures in the curriculum, a reduction in Irish-medium teaching, changing teacher attitudes and a lack of engagement by parents. The changing role of the Department of Education and Science in relation to Irish and the rapid evolution of new educational structures, have also have had negative effects. Implications for the revitalisation of Irish are discussed.