PISA studies reveal that the impact of socioeconomic status (SES) on student achievement varies significantly both across and within countries (Schleicher, 2014). Thus, a specific indicator measuring equity at the country level which is concerned with the impact that SES has on student achievement has been developed. It is argued that equitable educational systems are those where SES has a relatively small effect on student learning outcomes. Equity is seen as related to fairness which implies that personal or socio-economical characteristics such as gender, ethnic origin, or family background should not be obstacles to success in education (Field, Kuczera, & Pont, 2007). In this paper, we treat the effect of SES on student achievement as an indicator for measuring equity at the school and country level. We also investigate the relation of this indicator of equity with the quality dimension of effectiveness. Studies investigating differential teacher and school effectiveness reveal that teachers and schools matter most for underprivileged and/or initially low-achieving students (Kyriakides, 2007). Therefore, schools and countries which are effective in promoting student learning outcomes may at the same time be able to reduce unjustifiable differences in student achievement. The assumption that the dimensions of quality and equity at system and/or school level are related to each other is tested by conducting secondary analyses of PISA data and searching for differential effects of one of the indices used to measure the SES (i.e., HISEI) on student achievement. For each PISA cycle, a three-level (students within schools within countries) random slope model searching for differential effects of SES on achievement at the school and country level was used. The impact of SES was found to be smaller in countries and schools which were more effective in terms of the achievement of their students. Implications for research and evaluation are drawn.

Field, S., Kuczera, M., & Pont, B. (2007). No more failures: Ten steps to equity in education. Paris: Education and Training Policy, OECD. Kyriakides, L. (2007). Generic and differentiated models of educational effectiveness: Implications for the improvement of educational practice. In T. Townsend (Ed.), International handbook of school effectiveness and improvement (pp. 41-56). Dordrecht, the Netherlands: Springer. Schleicher, A. (2014). Equity, excellence and inclusiveness in education: Policy lessons from around the world. Paris: OECD.