The influences of schooling and everyday experiences on cognitive development are typically confounded. In the present study, we unraveled the influence of chronological age and years of schooling on the development of general cognitive competency in a two-wave longitudinal design with a three-year interval among 181 Kharwar children in India, aged 6 to 12 years. Effects of chronological age and years of schooling on cognitive development could be estimated independently because of their weak correlation among the Kharwar and because of the many shared background characteristics of school drop-outs, children without schooling, and children with schooling. The same five cognitive measures, each with parallel school and everyday testing modes, were administered to all children on both occasions. The internal structures of both the school and the everyday tests were equivalent across time and to each other. In line with our expectations, analyses of the net development per year revealed a decrement of the effect of chronological age, which was stronger for everyday tests than school tests, and an increment of the effect of years of schooling, which was stronger for school tests than everyday tests. Schooling ought to be considered in all theories of cognitive development, with genuine attention toward the real cognitive advantages it has at each developmental level.