Why are cognitive abilities of children so different across countries? The link between major socioeconomic factors and PISA test scores

Abstract
Path analysis was employed to examine the effects of socioeconomic factors on children's level of cognitive ability (measured by PISA scores) at a cross-country level (N = 55). The results showed that children's level of schooling had a positive direct effect on their cognitive ability, while the direct effects of adult fertility rate and child mortality were significantly negative. As we found that child mortality had the largest total effect on cognitive ability, the results also confirmed that per capita income had indirectly channeled its positive effect on cognitive ability through the reduction in child mortality. Moreover, in the long term, parents' education level had the largest positive indirect effect on cognitive ability because it significantly increased children's schooling rate and reduced the fertility rate. We suggest that, in the countries considered herein, well-educated parents have higher awareness of quality of life that indirectly raises the cognitive ability of their children.