Emerging STEAM (Science, Technology, Engineering, Art, and Mathematics) classrooms in K-12 schools across the United States have prompted researchers to begin questioning the impact of STEAM instruction on student achievement. This study examined the relationship between STEAM classroom instructional environment measures using a quantitative STEAM classroom observation form developed and piloted by the researchers and students’ achievement scores in mathematics and language arts using standardized achievement tests. Researchers captured multifaceted STEAM instructional strategies associated with creativity, critical thinking, communication, and collaboration skills using a numeric observation scale associated with four levels of intensity recorded by university trained research assistants. A series of Spearman Rho correlation procedures were performed to examine the relationship between the classroom observation data (independent variables) and state standardized achievement scores (dependent variables). These data were empirically connected to students’ achievement scores derived from state standardized testing data. Results provide an empirically-based rationale for assessing STEAM instructional practices using classroom observational data. Implications of empirically connecting STEAM instructional practices to student achievement outcomes may offer an action plan and methodology for school districts to use for capturing empirical evidence, thereby assisting schools and school districts grappling with STEAM funding challenges. Implications of the study may also provide evidence for researchers for determining: (a) effective STEAM instructional strategies; (b) purposeful STEAM professional development topics; and (c) strategic workforce preparation skills necessary for moving STEAM forward into a global community of learners.