School change is difficult and is both leveraged and hindered by interactive influences within complex systems of social practice. Whole-school STEM (science, technology, engineering, and mathematics) is a growing trend with unique aspects of change required of educators. A qualitative case study was used to analyze educator perspectives of the affordances and constraints to implementing a project-based, STEM-focused curriculum across all grades and classes of a rural school district in the United States. Educator journals and interviews informed the case over the first 1.5 years of the initiative. Identified affordances and constraints to implementation were organized into six factors and one element. "External," "teacher," and "curriculum" factors were disproportionately described as affordances, while "administration" and "district" factors were disproportionately described as constraints to the initiative. "Student elements" and "fixed" factors were identified as balanced between affordances and constraints. STEM-specific implications of these findings are discussed.