Inadequacies in the SES–Achievement model: Evidence from PISA and other studies

Abstract

Students’ socioeconomic status (SES) is central to much research and policy deliberation on educational inequalities. However, the SES model is under severe stress for several reasons. SES is an ill-defined concept, unlike parental education or family income. SES measures are frequently based on proxy reports from students; these are generally unreliable, sometimes endogenous to student achievement, only low to moderately intercorrelated, and exhibit low comparability across countries and over time. There are many explanations for SES inequalities in education, none of which achieves consensus among research and policy communities. SES has only moderate effects on student achievement, and its effects are especially weak when considering prior achievement, an important and relevant predictor. SES effects are substantially reduced when considering parent ability, which is causally prior to family SES. The alternative cognitive ability/genetic transmission model has far greater explanatory power; it provides logical and compelling explanations for a wide range of empirical findings from student achievement studies. The inadequacies of the SES model are hindering knowledge accumulation about student performance and the development of successful policies

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CONCLUSION

The paper critiques the dominant SES model used in the analysis of student achievement. The SES model is failing for several reasons. Its conceptualisation is muddled and contradictory. SES data collected from students are often unreliable, and both parental education and 'books in the home' are, to some extent, endogenous to student achievement. There is also a lack of consistency between the measured components cross-nationally and, in some countries, over time, so it is difficult to sustain the idea that the same concept is being compared. Despite its high profile among researchers and policymakers, SES has only moderate effects on achievement. Even the expansive ESCS measure in PISA explains only modest amounts of variance in PISA test scores. SES effects are likely to be, to a considerable extent, proxies for the effects of parental ability. It is no accident that policies that focus on such an ambiguous and poor explanatory concept as SES are not successful.

We are not arguing that the home environment is completely irrelevant to student performance. Very wealthy and high-income families can send their children to private schools, which increases the chances of university entry (Jerrim et al., 2016). Undesirable changes in home circumstances (e.g., job loss, divorce) can adversely impact student performance (Lehti et al., 2019; Nilsen et al., 2020). Parents influence their children in myriads of ways and most parents monitor their children's education. However, the overall impact of the home environment, SES and parenting are much weaker than commonly assumed. The problem is that the SES model has become an idée fixe among researchers and policymakers, and they insist that it explains much of the variance in student achievement, is theoretically credible, and is sensitive to policies that aim to reduce educational inequalities.

The cognitive ability/genetic transmission model provides more compelling explanations than the SES model. It accounts for the SES–achievement relationship, the small or negligible SES effects when controlling for cognitive ability or prior achievement, or in fixed-effects analyses, the increasing intradomain correlations, the sizeable interdomain correlations, educational differentiation, the enduring effects of PISA test scores on subsequent educational and socioeconomic attainments, and the existence of ‘resilient’ students. Teachers’ judgements of students’ aptitudes are based largely on their test performance, not SES or cultural signals. The cognitive ability/genetic transmission model does not require ad hoc additions to maintain basic plausibility. It can be part of a vibrant growing understanding of student performance.

Although there is a great reluctance among research and policy communities to admit that cognitive ability plays a substantial role in student performance, nonetheless teachers, schools and educational authorities implicitly acknowledge its importance. Teachers routinely allocate students to different learning groups and set work based largely on their prior performance. Most primary schools provide remedial teaching, and at higher grades advanced or extension classes. In middle secondary school, streaming in mathematics and science is not uncommon. In upper secondary school, students are allocated, or allocate themselves, to more and less academically demanding subjects. Some school systems formally track students either on entry to secondary school, or a few years later based largely on their prior performance. So, acknowledging the importance of general and specific abilities would not change the organisation and practices of educational institutions. However, it would change the rhetoric surrounding, and the implementation of, and most likely the success of, educational policies