Adjusted indicators of quality and equity for monitoring the education systems over time. Insights on EU15 countries from PISA surveys

In this work, we investigate how European countries belonging to EU15 are performing in terms of the quality and equity of their educational systems. To do so, we jointly analysed student competencies in mathematics and reading using data collected in four different waves (2006, 2009, 2012, 2015) by the Program for International Student Assessment (PISA) run by the Organisation for Economic Cooperation and Development (OECD). The aim of this analysis is twofold: (i) to assess the associations between students' competencies inmathematics and reading and their socioeconomic status and to investigate how this relationship varies across countries over time; (ii) to present a batch of adjusted indicators relevant to the investigation of educational performance over time in terms of quality (average student competencies) and equity (low association between student achievement and their socioeconomic backgrounds). We fitted a mixed-effect (multilevel) regression model with a bivariate latent structure and random intercepts and slopes to assess the effect of socioeconomic and cultural background on student competencies across countries over time and to assess the performance trajectories of EU15 countries with respect to European Commission benchmarks. We present and discuss our main findings and their implications in terms of the policies of EU15 countries.