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.