The TIMSS 2015 results revealed for the 8th graders in Sweden an improved math score. However, the achievement gaps with respect to socioeconomic and ethnic background also have increased dramatically (Mullis, Martin, & Loveless, 2016). Similar patterns of changes have been observed for other countries as well, so it is interesting and important to examine the factors that might be lying behind the observed trends in equity and efficiency. One possible explanation is that changing opportunities to learn (OTL) have had differential effects on equity and efficiency. Many countries have revised their curricula, and other reforms, such as implementing free choice of schools, may have changed the social ethnic composition of the schools. Changes in the learning and teaching environment may, furthermore, constrain or strengthen the OTL (e.g., Authors, 2016a; 2016b). In the study we focus on content changes in mathematics between 2011 and 2015 for all participating countries. We try to establish a causal link between the changing OTL and the changing achievement gaps between students of different social demographic and ethnic background. Cross-country comparisons are done by multiple-group two-level random coefficients model within the structural equation modeling framework. A country-level analysis with fixed effects across countries and time will also be tested to validate the results from the first set of analyses (Murnane & Willett, 2010). Preliminary analyses indicate that socio-economic and ethnic inequality in math achievement differ significantly across schools for some countries. The school-student mix too appears to have a varying effect on the between-school differences in the relationship between student’s socio-demographic characteristics and their math achievement. We expect that, in addition, differences in OTL between 2011 and 2015 have an effect on the sociodemographic inequality in math achievement across different educational systems. Implications for policy and practice as well as methodological implications are discussed. Improving educational equity and quality through balancing the school mix of students, as well as through the design of the implemented curriculum seem to be important considerations.

Authors (2016a) Authors (2016b) Murnane, R. J., & Willett, J. B. (2010). Methods matter: Improving causal inference in educational and social science research. Oxford University Press Mullis, V.S., Martin, M. O. & Loveless, T. (2016). 20 Years of TIMSS International Trends in Mathematics and Science Achievement, Curriculum, and Instruction. TIMSS & PIRLS International Study Center, Lynch School of Education, Boston College and International Association for the Evaluation of Educational Achievement (IEA). Scheerens, J. (2017). Opportunity to Learn, Curriculum Alignment and Test Preparation: A Research Review. Springer International Publishing.