Literacy is thought to influence profoundly the ways individuals think about and carry out practical tasks and, in doing so, to foster important social and economic changes. Adult literacy is usually measured by performance on school-like tests of text comprehension and production skills, the results of which are then correlated with outcomes of policy interest such as increased productivity. Such approaches necessarily reveal little about how individuals use literacy skills that may enhance productive capacities. Nor do they indicate much about the knowledge adults possess that enables literacy to become a truly functional cognitive skill. This article examines the relationship between school-acquired literacy and agricultural innovation in Kenya. Previous research has established a strong relationship between schooling and agricultural productivity in many African and Asian countries. Literacy, in combination with greater use of modern inputs, is the means of relating school to higher productivity. We investigate the interrelationship of these factors and show that, while schooling and literacy may promote reliance on modern inputs, capacities to use them safely and effectively depend on the cultivator's knowledge of modern science. Increasing years of schooling or performance on schoollike literacy tasks is not likely to increase agricultural productivity unless attention is also given to improving the quality of instruction students receive in science and other subjects.