This paper explores school level determinants of curriculum narrowing in the senior phase of secondary education, under the Scottish Curriculum for Excellence (CfE). It presents findings from an analysis of longitudinal administrative education data (2011–2017), and Scottish Qualifications Authority (SQA) data on subject enrolments for Scottish Credit and Qualifications Framework National 5 level qualifications, undertaken by 14–15‐year‐old students in year 4 of secondary education (S4) in Scotland. The data are aggregated at the level of schools and linked with Scottish School Census data that provide information about school characteristics (in terms of their size, number of qualified teachers, socio‐economic composition, etc.) and school area characteristics. We used descriptive methods of statistical data analysis and multilevel regression modelling, in order to explore the variations between schools in: (a) number of subject choices; and (b) configuration of subject enrolment and to identify factors responsible for these variations. Our findings show that the senior phase curriculum is becoming narrower. There is trend since 2013, the year when new qualifications under CfE were introduced, for fewer subjects to be taken in school year S4 for level 5 National Qualifications. Yet, the size of this reduction has not been uniform, but has varied between schools of different characteristics, between areas with different level of deprivation and between local authorities across Scotland. The findings show that the SES composition of school intake has a strong association with the number and configuration of subject entries. A larger reduction in the number of subject entries for National 5 level qualifications took place in schools in more deprived areas, as well as in schools with a larger number of students from disadvantaged socio‐economic backgrounds, schools where the proportion of pupils with additional learning support needs was higher, and schools with poorer staff–student ratios. We also found that the number of subject entries was smaller in schools where the overall number of subjects offered for National 5 level qualifications was smaller. Furthermore, we found that schools in areas of higher deprivation and schools with larger numbers of pupils from disadvantaged backgrounds had smaller proportions of young people enrolled in Sciences and Modern Languages, and a larger proportion of pupils enrolled in Vocational subjects.