Democratisation, economic development and academic achievement are significant social dimensions which are potentially interrelated. The current article aims to contribute to a more comprehensive understanding of the relations between these three dimensions by taking advantage of data from the Programme for International Student Assessment (PISA), including the 2018 and 2022 surveys. The regression and mediation models were based on both individual level data (eight countries across diverse regime types) and cross-country level data (N = 77 in 2018, 81 in 2022). The results suggest that there were direct effects between income and democratisation across both surveys and analytical levels. The role of academic achievement is less definitive but does not mediate the relations between income and democratisation, although it predicts country-level income.