Purpose: Chile has developed the school improvement networks (SINs) strategy to support the work of school leaders. The purpose of this paper is to analyze the functioning and effect of the SINs strategy as perceived by principals and curriculum coordinators across the country. Design/methodology/approach: An adapted version of the Educational Collaborative Network Questionnaire was applied to a sample of 1,723 participants from 1,375 schools distributed in 398 networks. Descriptive, factor and sub-group statistical analyses by school performance categories and by different roles within these schools and networks are presented. Findings: Results indicate that school leaders perceive SINs as an opportunity to work effectively in shared projects that can later be implemented in their own schools. Participants indicate that they can share knowledge in their networks and use it to solve problems in their own schools, which is especially relevant for secondary school leaders who work in difficult circumstances. Results suggest that it is important to facilitate greater autonomy for school leaders in their networks, especially regarding decision making about network goals and activities that are more significant to their contexts. Originality/value: This is a national study of a recent school improvement strategy, which provides evidence, from the perspective of school leaders, of its strengths and improvement areas. This study shows that despite being in a competitive context, principals and curriculum coordinators value the opportunities to learn from and with others. These results can be of value for other contexts attempting to promote school networks as a means for school and system improvement.