Teachers are the most important resource in today's schools. In every country, teachers' salaries and training represent the greatest share of expenditure in education. And this investment in teachers can have significant returns: research shows that being taught by the best teachers can make a real difference in the learning and life outcomes of otherwise similar students. Teachers, in other words, are not interchangeable workers in some sort of industrial assembly line; individual teachers can change lives - and better teachers are crucial to improving the education that schools provide. Improving the effectiveness, efficiency and equity of schooling depends, in large measure, on ensuring that competent people want to work as teachers, that their teaching is of high quality and that high-quality teaching is provided to all students. This report, building on data from the Indicators of Education Systems (INES) programme, the Teaching and Learning International Survey (TALIS) and the Programme for International Student Assessment (PISA), explores three teacher-policy questions: How do the best-performing countries select, develop, evaluate and compensate teachers? How does teacher sorting across schools affect the equity of education systems? And how can countries attract and retain talented men and women to teaching?