When the earliest Irish language immersion schools outside Irish-speaking (Gaeltacht) areas were established, students were likely to come from relatively high socioeconomic backgrounds. While research has shown positive outcomes for these students, less is known about the outcomes of immersion education for students from areas of social disadvantage. Of 145 Irish immersion primary schools in the Republic of Ireland in 2016, 13 (8%) served low socioeconomic status (SES) communities. The current study examined the achievements of Grade 3 (n. = 283) and Grade 6 (n. = 235) students in these schools on nationally-standardised tests of English reading and mathematics. Their scores are compared to those of students attending schools in areas of disadvantage nationally. Immersion students in Grade 3 achieved lower mean scores on both English reading and mathematics when compared with their low-SES English-medium peers. However, Grade 6 students achieved at about the same level in mathematics and outperformed their low-SES peers nationally in English reading.