Surging inequality is a defining feature of the world children grow up in today. The neighborhood they live in stages a primary developmental context where this feature of our present time plays out. Children’s demographic and socio-economic status (SES) is given by the status of their parents. Parental and neighborhood SES is associated with child mental health and educational performance, and childhood is a vulnerable period. To understand how and why early life socioeconomic position is linked to mental health and educational performance, I propose a groundbreaking paradigm generalizing temporal, spatial, social, genetic, and individual levels of inference. I will do this by having genomically similar children growing up in different families at different places at different times. These multitudes of counterfactuals will allow me to jointly evaluate hypotheses on selection and causation and risk and protection factors for mental health and academic outcomes. The GeoGen study will render a new understanding of (a) how transmission of risk is transmitted across generations, (b) how early mental health is an antecedent of academic failure, (c) the interactions between genetic risk and protective contextual factors, and (c) characteristics of schools and neighborhoods that are optimal for children’s psychological development. I will use Norway since 1940 as a laboratory (n=8 400 000) with registries giving full genealogy and year-by-year event data on place of residence, indicators of SES, mental health, and educational performance. Within this, I will nest a population-based cohort study comprising genotyping of families (n=240 000 in 110 000 families) and a wide array of survey data, such as non-cognitive skills. The combination of having data on all people in all schools and neighborhoods over time allows me to do an unprecedented study on the gene-environment interplay between risk and protective factors for mental health and academic outcomes.