The Elementary and Secondary Education Act (ESEA), as amended by the Every Student Succeeds Act (ESSA; P.L. 114-95), specifies the requirements for the state assessments that states must incorporate into their state accountability systems to receive funding under Title I-A. Title IA of the ESEA authorizes aid to local educational agencies (LEAs) for the education of disadvantaged children. Title I-A grants provide supplementary educational and related services to low-achieving and other students attending elementary and secondary schools with relatively high concentrations of students from low-income families. As a condition of receiving Title I-A funds, states, LEAs, and public schools must comply with numerous requirements related to standards, assessments, and academic accountability systems. All states currently accept Title I-A funds. For FY2017, the program was funded at $15.5 billion. While many of the assessment requirements of the ESEA have not changed from the requirements put into place by the No Child Left Behind Act (NCLB; P.L. 107-110), the ESSA provides states some new flexibility in meeting them. The purpose of this report is to describe the general assessment requirements of the ESEA as amended and discuss the new flexibility states have in meeting these requirements. The report also discusses some issues related to the changes enacted by ESSA regarding the use of assessments in accountability systems that are receiving attention as they are implemented. More specifically, this report examines issues related to assessment of student growth, assessment of students with disabilities and English learners, the use of computer adaptive assessments, student assessment participation requirements, and testing burden. While these changes have the potential to add flexibility and nuance to state accountability systems, states face the challenge of implementing them in such a way as to maintain the validity and reliability of the required assessments.