A limited number of highly selective high schools specializing in science, technology, engineering and mathematics (STEM) education have existed for many decades, encouraging youth with identified STEM talent to pursue careers as STEM leaders and innovators. As members of the National Consortium for Specialized Secondary Schools of Mathematics, Science, and Technology (NCSSSMST), many of these selective schools benefit from scholarly interaction and dialogue on how to best serve their students. However, research on selective STEM schools has largely been limited to internal program evaluation, making it difficult to assess any causal inferences related to effective school features and practices. The purpose of the study was to gather a nationally representative sample of administrators' and teachers' perceptions about practices and policies to help identify and assess the critical components (Lynch et al., 2013) of STEM-focused education. The authors conducted an extensive search to identify the sampling frame of STEM high schools throughout the United States. They identified a total of 949 unique STEM schools by searching websites, reviewing articles identified through electronic searches using key search terms, contacting state departments of education, and soliciting names of schools from the National Consortium of Specialized Secondary Schools of Mathematics, Science, and Technology. These schools served as the sample for the study. To develop the STEM administrator and STEM teacher survey for the study, they first observed and interviewed key stakeholders (teachers, students, and administrators) in 12 STEM high schools. Using the qualitative data from these visits, they inductively coded a comprehensive set of curricular and instructional strategies and practices, school policies, and school culture factors that were present at the STEM schools. Common features across schools, especially those that seemed to represent best practices in STEM education based on the literature, were developed into item stems for the surveys. The 48-item administrators' survey was divided into five sections: Professional Culture, Curricular and Instructional Practices, Policies and Procedures, Description of Practices, and Demographics. The 41-item STEM teacher survey was comprised of four sections: School Climate, Curricular Approaches, Instructional Strategies, and Learning Environment. The authors sampled all 949 identified schools by sending hard copy and electronic versions (via e-mail links) of the survey to each site. The National Research Council (2011) established three broad goals for K-12 STEM education in the United States: expand the number of students who ultimately pursue advanced degrees and careers in STEM fields; expand the STEM-capable workforce; and increase science literacy for all students. Effective instruction and conditions and cultures that support learning (National Research Council, 2013) were identified as the two most proximal influences that should enable students to attain these goals. This study's findings indicated that teachers and administrators rated many related survey items as very important or essential, but the frequency of some practices did not match their perceived importance.