Teacher quality is the single most important lever schools have for raising student achievement. A substantial body of research indicates that new teachers are less able than their more experienced colleagues to help students fulfill their academic potential. Yet in many school districts—particularly those in urban settings—as many as half of the teachers may have less than five years’ experience. In addition, the students who face the greatest challenges are most likely to be assigned novice teachers. By supporting new teachers, increasing their effectiveness, and reducing turnover, school districts can give the children most in need of high-quality teaching a real chance at success. In this practical yet visionary book, Ellen Moir and her colleagues at the New Teacher Center review what current research suggests (and doesn’t) about the power of well-designed mentoring programs to shape teacher and student outcomes. They set forth the principles of high-quality instructional mentoring and describe the elements of a rigorous professional development program. Detailed case studies show how these principles can be applied at the district level and highlight the opportunities and challenges involved in implementing these programs in different contexts. The book makes a powerful case for using new teacher mentoring as an entry point for creating a strong professional culture with a shared, aligned understanding of high-quality teaching.