No Child Left Behind (NCLB) was a U.S. law enacted in 2001 aimed at improving educational outcomes for all students. It emphasized standardized testing to measure student progress and required schools to meet specific performance goals. Schools that failed to meet these goals faced consequences, including loss of funding or restructuring. The law aimed to close achievement gaps between different groups of students, particularly those from low-income families and minority backgrounds. While it increased accountability in education, it also faced criticism for its heavy reliance on testing and for not adequately addressing the needs of all students.