An adequate level of linguistic complexity in learning materials is believed to be of crucial importance for learning. The implication for school textbooks is that reading complexity should differ systematically between grade levels and between higher and lower tracks in line with what can be called the systematic complexification assumption.…

Prior research has shown that quantity of schooling affects the development of intelligence in childhood and adolescence. However, it is still debated whether other aspects of schooling--such as ability tracking or, more generally, school quality--can also influence intelligence. In this study, the authors analyzed intelligence gains in academic-…