Assessing Opportunities to Learn (OTL) implies the measurement of different aspects of the curricular implementation in the classrooms, such as the contents that the teacher selects for the course and the time of exposure and the frequency of the tasks proposed. Based on recent studies that demonstrate the influence of this curricular dimension on students' performance, this work analyzes the relationships between the emphasis made by teachers of third grade of secondary school on different reading contents, and students' performance in reading tests. The aim of this research is to establish the effect of the emphasis with which teachers propose different types of reading activities (literal, inferential, and critical) on students' performance. From the analysis of compositional data, this study concludes that the students of those teachers who report working a greater extent on the critical dimension of reading obtains--on average--higher scores on the national reading test. This result holds even when socio-economic and cultural context and reading habits are controlled for. [For the full proceedings, see ED607784.]