<p>Undergraduate students often struggle with scientific communication, particularly in writing clear and concise lab reports. A retrospective cohort study was conducted in a multi-section Anatomy and Physiology laboratory course to examine patterns in student writing performance and perceptions of science writing following the implementation of an online guided writing module. The module, developed in Nearpod integrated with Canvas, provided task-specific instruction and embedded questions with immediate feedback focused on authoring a results section for a lab report assignment. Student enrolled during the 2024 implementation term who completed the module (<i>n</i> = 278) demonstrated higher lab report writing scores compared to students in prior academic years (2022 (<i>n</i> = 344), 2023 (<i>n</i> = 335)) after controlling for overall course grade and the effect of different instructors. In addition, the number of students receiving failing grades on the assignment declined during the 2024 term. Student survey responses indicated that students perceived the module to be helpful with the majority reporting increased confidence in completing the assignment. These findings suggest that online guided writing modules may support student writing performance and writing self-efficacy under authentic learning conditions in multi-section courses.</p>