About 17% of the variance in PISA science scores is explained by students’ socioeconomic background, compared to an OECD average of 12.9% (OECD, 2016a). This is again consistent with results from the national SIMCE assessment. Among students in Year 4, students from high SES households score 26% higher in mathematics and 22% higher in language than students from low SES households. According to a study conducted by the Ministry of Education this difference is in part due to the fact that students in technical-professional programmes have fewer hours of instruction of general education than their peers in scientific-humanistic programmes (Ministry of Education, 2013).