In sub-Saharan Africa, just over two-thirds of girls complete their primary education and four in ten complete lower secondary education. More needs to be done to improve educational opportunities for girls, which would help end child marriage and boost countries’ economic development. The first part of this study updates and expands for a much larger number of countries a previous investment case on the benefits of educating girls and ending child marriage. The second part looks at the role of teachers and school leaders in improving learning outcomes and educational attainment for girls. While the literature emphasizes economic incentives for adolescent girls to remain in school, it is also important to note that: (1) Lack of learning is a key factor leading to drop-out in primary and lower-secondary school; (2) Teachers and school leaders are key to improving learning, but new approaches are needed for pedagogy in the classroom and for training teachers and school leaders; and (3) Nationally, professional standards and competencies for teachers and school leaders are also required. These three simple facts call for investing in teachers and school leaders, especially women, to improve education for girls and end child marriage.