This study aims to analyse the impact of ten dimensions of the education service process in the municipalities of São Paulo, Brazil, on students’ performance (the education service outcome) – assessed by the IDEB scores. The ten process dimensions are divided into four areas of school educational service: human resources, which covers (1) training hours, (2) academic background, and (3) teachers’ salary; capacity, which includes the (4) number of students per class and the (5) number of students per teacher; infrastructure, which covers the (6) number of computers per school and the (7) number of libraries and study rooms; and, at last, administrative practices, which includes (8) the use of nutritionists, (9) the use of teaching materials and handouts, and (10) the use of uniforms. In order to identify which of the process dimensions impact on the final IDEB scores, a multiple linear regression model was developed. The result showed that of the ten dimensions, six are in fact relevant to the quality of education service – the teachers’ academic background, teachers’ salary, the number of students per teacher, the number of computers per school, the number of libraries and study rooms, and the use of teaching materials and handouts. This conclusion is especially important because it assists in the decision of resource allocation in the field of public education, which might already be scarce.