This action research explored how Year 12 achievement data were used by school personnel to inform practice within seven Catholic secondary schools. Deputy Principals of Curriculum from participating schools were interviewed regarding their perceptions of the improvement of Year 12 student achievement outcomes, and their insights into how to strengthen future efforts (or achievements). Three key insights included: Communication of achievement data to key stakeholders in the school community, strategic use of achievement data by teaching staff, and leadership strategies to promote an achievement culture to the students. The findings of this research will serve to improve and strengthen practice at participating schools and to stimulate discussions in other schools about the effective use of achievement data.