Signed into law in December 2015, the Every Student Suceeds Act (ESSA) offers state education agencies significant opportunities to use evidence to support the improvement of schools and ensure better outcomes for all students. ESSA replaces the law, regulations, and guidance established through the 2001 No Child Left Behind Act (NCLB), but two elements of the new legislation stand out: (1) the shift away from federal mandates toward greater state and local authority; and (2) the emphasis on evidence-based school improvement practices. This report addresses this second element by clarifying the definition of "evidence-based" that ESSA uses, distinguishing it from the "scientifically based research" provisions of NCLB and providing a framework for how state education agencies can maximize collaborative efforts to implement evidence-based school improvement practices. In summary, the evidence-based approach encourages state and district leaders to consider multiple tiers of evidence and examine the strength of the evidence in making decisions. On the other hand, scientifically-based research sets a very specific, narrow standard for acceptable evidence. These two terms will also be examined in this report.