It incorporates lessons from other international studies, inputs from the participating countries and many elements from the PISA questionnaires. For example, questions about school infrastructure and teaching and learning materials are related to student performance in high-income countries, but are often unrelated to differences in performance in middle-income countries (Lockheed, Prokic-Breuer and Shadrova, 2015). In addition, the measure of economic, social and cultural status used by PISA does not adequately capture lower levels of parental education and income or the risk factors associated with poverty that are more frequent in low-income countries. For example, the questionnaires collect more detailed data on students' language of instruction at school, language at home and their socio-economic status, as measured by home possessions and parents' education, literacy skills and participation in the labour force.