First introduced in 1965, the Elementary and Secondary Education Act (ESEA) has evolved over nearly five decades, emphasizing education reform priorities that mirror the changing national education policy conversation. The most recent iteration of ESEA, also known as the No Child Left Behind Act (NCLB), was enacted in 2001. It emphasized improving outcomes for all students regardless of their race, language, or disability, with a strong focus on accountability for schools and districts. A decade later, ESEA is again due for reauthorization. This Pocket Guide will assist policymakers and educators as they consider changes to this law--particularly changes related to improving low-performing schools. (Contains 1 footnote.) [For related reports, see "Students with Disabilities: A Pocket Guide. Reauthorizing ESEA: Making Research Relevant" (ED530795) and "Educator Effectiveness: A Pocket Guide. Reauthorizing ESEA: Making Research Relevant" (ED530794).]