This article aims to analyse the related factors of students on reading performance. The sample is composed of 8,551 students in year 4 of primary education (52.1% boys, 47.9% girls). A Confirmatory Factor Analysis (CFA) was carried out and a multilevel model was calculated on PIRLS student questionnaire comprising 28 items. The results show the interrelationship between the five factors with the greatest influence on performance: students’ attitude towards reading, students’ wellbeing at school, the quality of teaching, students’ reading difficulties and reading self-efficacy.