No evidence for cumulating socioeconomic advantage. Ability explains increasing SES effects with age on children's domain test scores

Studies that investigate the effects of socioeconomic background (SES) on student achievement tend to find stronger SES effects with age, although there is much inconsistency between studies. There is also a large academic literature on cumulative advantage arguing that SES inequalities increase as children age, a type of Matthew Effect. This study analysing data from the children of NLSY79 mothers (N ≈ 9000, Obs ≈ 27,000) investigates the relationship of SES by children's age for two cognitive domains (Peabody Picture Vocabulary test and digit span memory) and three achievement domains (reading comprehension, reading recognition and math). There are small increases in the SES-test score correlations for several domains, but there are more substantial increases in the test score correlations with mother's ability and prior ability. Regression analyses found linear increases in SES effects for all domains except digit memory. However, when considering mother's ability, the substantially reduced SES effects did not increase with children's age. Much of the effects of SES on children's domain scores are accounted for by mother's ability. The effects of prior ability also increase with age and SES effects are small. Therefore, there is no evidence for cumulative socioeconomic advantage for these domains. Generally, increases in SES effects on children's cognitive development and student achievement are likely to be spurious because of the importance of parents' abilities and their transmission from parents to children.