Improving student learning in our country's highest need schools is and endeavor that is challenging, complicated, and imperative. The major school reform efforts of the last few decades have largely failed to influence student achievement or to impact the ever-widening achievement or opportunity gap. These disappointing results have led policymakers, foundations, districts, and educators to search for remedies, many of which focus on teacher competence and accountability. While discussions of education reform rightly turn to the influence of teachers, there are various views regarding how best to involve teachers and what effective teacher involvement requires. To inform this debate, this study explores the concept of teacher ownership -- that is, a teacher's sense of alignment with an improvement effort and agency to influence it. The study aims to measure how teachers experience this sense of ownership, the conditions and supports that most allow for it, and how it can help effect meaningful change in schools. The study examined a network of schools within the Los Angeles Unified School District (LAUSD) that is working to transform and ameliorate educational inequalities by broadening students' learning opportunities.1 Through the implementation of one or more of three approaches -- community schools, Linked Learning, and Promise Neighborhoods -- these schools are striving to ensure that all students graduate ready for college, career, and civic life. Findings indicate that teacher ownership exists where: (1)Teachers are able to co-construct knowledge and influence and lead school improvement efforts; (2) Supports and practices are in place that allow teachers to break down barriers and work collectively to build system coherence; and (3) A school's culture values teachers' collective expertise and knowledge and recognizes that schools are social and cultural, as well as academic, institutions. Important insights into policies that can support and strengthen teacher ownership are detailed. Implications for policy and practice are discussed. [For the executive summary, see ED574744.]