Efforts to improve student learning in K-12 education in the US are not new; however, educational research has traditionally focused on individual components of schools (e.g., teacher professional development, leadership, social relationships, programs, curricula) targeting teachers to improve student learning. While these innovations provide hope for change, they are limited in their focus and application to other school settings in that school contexts are unique to the individuals making them up and the collaborative missions and goals they pursue. To foster capacity for teachers to implement instructional reforms (i.e., how teachers teach), research must be focused on a holistic interpretation of the school as an organization. This study developed and validated a survey to examine elementary teachers’ science and mathematics instructional practice use as well as their perceptions of instructional reform capacity within their school environment from an ecological organization perspective. Over 300 elementary teachers from a large urban district participated in the survey over the course of four weeks. Findings indicated elementary teachers utilized teacher-centered instructional practices more frequently than reform-oriented (i.e., student-centered) instructional practices. However, teachers reported more frequent use of instructional practices in their mathematics lessons compared to science lessons. Furthermore, data was used to investigate the underlying dimensions of instructional reform capacity and examine the relationship between those dimensions and instructional practice use both within and between subjects (i.e., science and mathematics). Results revealed dimensions underlying instructional reform capacity as well as correlations with instructional practice use are not the same for elementary science and mathematics. Dimensions of professional learning, structure, and policy were more strongly correlated with reform-oriented (i.e., student-centered) instructional practices. Implications from these findings suggest the necessity of a more holistic perspective of instructional reform capacity to better support instructional reforms across subject areas in schools, on both the local level and within research.