Collective teacher efficacy (CTE) refers to the collective perception in a school that teachers make an educational difference to their pupils over and above the impact of their social circumstances. This study explored the relationships between CTE, socio-economic status (SES) and pupil attainment levels in reading, writing and mathematics (at the whole primary school level). Sixty-six teachers in 15 out of 19 schools in a small Local Authority participated. Significant positive relationships were found between SES and attainment in reading and mathematics (but not writing). However, significant positive relationships were also found between CTE and attainment in reading and writing (but not mathematics). Neither SES nor CTE independently accounted for a statistically significant proportion of the total variance in attainment. However, CTE appeared to have a much stronger independent impact than SES in writing (and also a modest independent impact in reading). One school with an atypical pattern of high CTE and high attainment despite low SES was studied in depth. Here, school climate or ethos, high quality in-service training and a focus upon pedagogy were perceived as the most potent factors in raising attainment. When these factors serve to heighten CTE, the impact of SES on pupil attainment may be reduced, and this may be easier in some subjects than others.