The research on washback of a test has little been carried out in Korea while it has been flourishing in language testing researchers overseas. This paper investigates whether the advent of NEAT has affected the perception of test takers and the teaching/learning practices in English classrooms of Korea. In addition, we also want to investigate the relationship between variables such as perception of test users, teaching/learning practices, and test scores. We carried out a survey with 601 students who were seated at NEAT administered in April 2013 as well as 3,267 third-year high school students who had no experience on NEAT. The analyses revealed some evidence to support that NEAT has an effect on the perception of the participants. However, the analyses also revealed that NEAT was not effective to appeal for a change in teaching and learning practices in English classrooms in Korea.