Background Cattell’s Gf–Gc distinction is quite generally recognized. However, the developmental part of the Gf–Gc theory of intelligence has not gained the same recognition. Results are inconsistent, but recent discussions emphasize the importance of homogeneity of samples with regard to education and language when investigating the developmental Investment theory. Aims The aim of this study was to investigate the influence of Gf and Gc on the development of knowledge and skills in a sample of children in compulsory school who are homogenous with regard to level of education, age, and cultural background. Sample Totally, 9,002 individuals from the evaluation through follow-up database born in 1972 and who left compulsory school in 1988 were included. These individuals were followed up in Grades 3, 6, and 9. Methods Structural equation modelling was used, and autoregressive path models were fitted. All modelling was performed using Mplus version 6.1. Results In the first step, a path model with a simplex structure was defined. However, a second model with direct relations of Gf on Gc in Grades 6 and 9 had better model fit, suggesting a continuous influence of Gf on Gc. However, no direct influence of Gf was found for the subject grades. Conclusion Due to the continuous influence of Gf on the measures of Gc throughout compulsory school, support for Cattell’s (1987) Investment theory was found.

Research has found that grades are the most valid instruments for predicting educational success. Why grades have better predictive validity than, for example, standardized tests is not yet fully understood. One possible explanation is that grades reflect not only subject-specific knowledge and skills but also individual differences in other aspects. The purpose was to investigate the relative importance of knowledge and skills and other aspects encapsulated in grades for the predictive validity of compulsory school grades for educational success in upper secondary school. Structural equation modelling was used. Participants were 9th-grade students from 3 birth cohorts, each comprising full populations of approximately 100,000 students. The results showed that the subject-specific factors and an additional common grade factor contributed to the predictive validity. Effects of gender and parents' education were found in the common grade factor, with girls and students with a lower educational background being advantaged.

Irrespective of the grading system, grades are the most valid instrument for predicting educational success. Previous studies have shown that criterion-referenced compulsory school grades are multidimensional, reflecting subject-specific dimensions and a common grade dimension, both of which contribute to the predictive validity of grades. This suggests that in addition to knowledge and skills, grades reflect other aspects which might have importance for the prediction of educational success. The purpose of this study was to investigate, using structured equation modeling, whether norm-referenced compulsory school grades display similar patterns of dimensionality and predictive validity to criterion-referenced grades. Possible differences due to gender and parents’ education were considered. Participants were 3855 students born in 1972. The results showed that norm-referenced grades are multidimensional, and that both the subject-specific and common grade dimensions contribute to predicting educational success. In the common grade dimension, girls and students with higher educational backgrounds were favored.