Using a genetically sensitive design, we investigated the etiology of academic performance in Science in elementary school, and its etiological links with other academic abilities and general cognitive ability ("g"). The sample consisted of over 2000 pairs of twins at 10 years of age from the Twins Early Development Study. Science performance, as rated by teachers, is moderately heritable (49%) and shows only modest shared environmental influence (27%). Our multivariate results show that Science shares genetic influences with English, Math and "g." Nonetheless, Science is more than just "g," as there are specific genetic and environmental influences on Science. In addition, there are common environmental influences shared by the three school subjects that are not shared with "g"--a school environment effect. (Contains 5 tables and 2 figures.)