Reforming instruction is challenging. In this comparative case study of 12 school districts, we investigated the dilemmas that emerged for system leaders as they engaged in system building for elementary science and the approaches leaders took in managing them. We found that system leaders' efforts to manage their environments contributed to the preferential treatment of literacy and mathematics relative to science. Leaders managed this dilemma using three strategies: (a) integration of science with other subjects, (b) specialization of teachers, and (c) adopting curriculum materials. This study contributes to literature on dilemma management by showing that dilemmas in education system building are school-subject sensitive, emerge in relation to system building for other subjects, and are embedded in school and education systems' structural/organizational arrangements.