Pre-service teachers are often required to evaluate lessons, as part of their development as reflective practitioners. The purpose of this action research was to improve student teachers’ critical thinking and evaluative practice, following external comments that this aspect should be strengthened. Utilizing a qualitative method approach, a textual analysis of the quality of the lesson plan evaluations produced over one academic year revealed that, in-line with the literature (Halpern, 1999), student teachers benefited from structured training, encouragement to use critical thinking skills and clear success criteria to enable them to monitor, assess and discuss their own progress. However, it was necessary to revisit critical evaluation several times over the year to support their development as effective, reflective teachers