Policymakers have been concerned with improving student achievement. Some have advocated that teacher quality is the means to increase student achievement, since teachers are critical in the learning process. One difficulty in ensuring that all students have quality teachers is that there is not an accepted definition of teacher quality, or of the characteristics that comprise it. There is also no consensus of how to measure teacher quality. This book examines teacher quality cross-nationally using consistent and comprehensive measures to assess the level, variance, association with students socio-economic status, and the effects of teacher quality upon mathematics achievement. The analysis sheds light on the difficulties in measuring teacher quality, the need to generate better data, and use refined methodology to improve the measurement of teacher quality in order to more accurately assess its effects. The literature review and analysis in this book are particularly useful foreducational and comparative researchers, as well as policy makers.