Based on a large-scale international study of teachers in Los Angeles, Chicago, Ontario, and New York, this book illustrates the ways increased use of high-stakes standardized testing is fundamentally changing education in the US and Canada with a negative overall impact on the way teachers teach and students learn. Standardized testing makes understanding students' strengths and weaknesses more difficult, and class time spent on testing consumes scarce time and attention needed to support the success of all students—further disadvantaging ELLs, students with exceptionalities, low income, and racially minoritized students.