This study provides preliminary evidence from an Italian in-service training program addressed to lower secondary school teachers which supports school improvement plans (SIPs). It aims at exploring the association between characteristics/contents of SIPs and student improvement in math achievement. Pre-post standardized tests and text analysis of SIPs were performed regarding a sample of 248 schools (13,816 students) participating in the project. Results show differences in planning strategies: better school improvements are associated with the ability to carry out a careful analysis of the context, prioritize elements in the diagnostic phase of the process and detect specific improvement goals.