The purpose of this report is to provide a synthesis of the research on K-12 testing accommodations. In this report, we summarize the research published in 2017. Previous reports by NCEO have covered research published since 1999. During 2017, 14 research studies were published on the topic of testing accommodations in the elementary and secondary education system. The academic literature described here encompasses empirical studies of performance comparability and validity studies as well as investigations into accommodations use, implementation practices, and perceptions of the effectiveness of accommodations.