The five-paragraph theme, while widely used by writing instructors, has often been criticized for its tendency to focus on a rigid formula rather than a writer's ideas. This study investigates the decision of an early-career teacher, Leigh, to teach her eighth-grade students the five-paragraph model in the context of a state-mandated writing assessment that rewarded such writing. The key settings for Leigh in learning to teach were her structurally fragmented teacher education program, her relationship with her mentor teacher during student teaching, and, as she embarked on her first teaching job, her entry-year supervisory committee and her English department colleagues. Through an activity-theory analysis of field notes, observation-based interviews, and other data, we interpret Leigh's decision-making as a function of her participation in tool-mediated action in these settings. Leigh's teaching was affected by forces without (e.g., community expectations to produce passing scores on the state writing test) and within (e.g., her colleagues' pressure on Leigh to teach to the test). These pressures superseded the motives of other settings in which Leigh participated, primarily her administration's downplay of the need to teach to the test. The study concludes with a reflection on why Leigh in particular and other teachers in general find this form useful enough to serve as a primary tool in their approach to teaching writing. (Contains 1 table and 1 note.)