We describe teacher fidelity (adherence to the components of the treatment as specified by the research team) based on a series of studies of a multicomponent intervention, Promoting Acceleration of Comprehension and Content Through Text (PACT), with middle and high school social studies teachers and their students. Findings reveal that even with highly specified materials and implementing practices that are aligned with effective reading comprehension and content instruction, teachers' fidelity was consistently low for some components and high for others. Teachers demonstrated consistently high implementation fidelity and quality for the instructional components of building background knowledge (comprehension canopy) and teaching key content vocabulary (essential words), whereas we recorded consistently lower fidelity and quality of implementation for the instructional components of critical reading and knowledge application.