Background/Context: Research underscores that school improvement relies on leadership that stretches beyond a principal, but significant developments to the design of school level leadership lags. This paper shares data and interpretations of school leadership organized as a network of formalized teacher-leader roles that are ranked, titled, and differently paid. Purpose/Research Question: The study examined the functions, tasks, and boundaries of different teacher-leader roles as well as teachers' perceptions of their legitimacy and value. It also explored whether formal roles generated negative side effects on school climate or teacher relations. Focus of Study: Ongoing skepticism of role formalization and ranking within teaching directed the study's attention to an extensive empirical case of formalization. Setting: Data were collected from eight secondary schools in England, where formalized teacher-leader roles are long established and associated with school performance. Research Design: The study was designed as a descriptive investigation of a leader system. It was conceptually framed by perspectives on schools as organizations and literatures on role formalization, leadership, and school improvements. Data Collection and Analysis: Observation, artifact, and interview data were collected. Description and analysis focused on the design of leader roles, the activities and conditions they generated, and school member perceptions of their legitimacy and value. Findings/Results: Formal roles that blend teaching with instructional and managerial leadership gain legitimacy and pass tests of goodness and value for teachers when they directly contribute to teachers' day-to-day work and success, as when they elevate working conditions, bring disciplinary knowledge and local understandings to learning and problem solving, and contribute to individual and collective efficacy. Conclusions/Recommendations: Networks of formal teacher-leader roles can bring more substantial and reliable resources to the conditions of teaching and school organizations than informal leadership or targeted coaching roles. Fears of negative social and professional consequences do not emerge when roles remain rooted in teaching, when leaders' tasks flow across logistical, instructional, and social dimensions of teachers' work, and when norms emphasize help and reciprocity.