K-12 engineering is a critical platform for achieving integrated science, technology, engineering, and math STEM teachingand learning in the Unites States. This has fueled research in the development and testing of integrated STEM curricula.This study examines the contrasting ways in which a prescribed curriculum is translated into practice. The study examinesthe implementation of 12-week secondary engineering unit (helmet design) by a teacher with high content knowledge inengineering in a rural/suburban school with 20 students. The unit was designed with significant input from a university-based team including content experts, learning scientists, master teachers, classroom teachers, and school districtadministrators as part of a grant focused on the creation of a high school engineering course. Five strands were identifiedin the unit for analysis: assessment, activities, apparatus, technology, and standards. Findings indicate much alignmentwith apparatus, standards, and technology strands and disparity within the assessment and activities strands between theprescribed unit and its enactment in the course by the teacher.