This research was conducted online at a private senior high school due to the Covid19 pandemic. Students' academic achievement plays an important role in students' lives because it impacts students' development in society. Based on the research, it was found that most of XII-Social students' academic achievements were low. Therefore, to improve students' academic achievement, the researcher implemented retest to provide retrieval practice and feedback for better learning, which was hoped to improve students' academic achievement. This paper aims to describe the way implementation of retest can improve students' academic achievement and the factors that influence students' academic achievement. The method used is descriptive qualitative. Moreover, the implementation of retest called every Christian teacher to be involved in transformational learning, in which it is not only focusing on students' academics but also their spiritual growth. The result obtained from this research was that the implementation had not shown a significant improvement in students' academic achievement. Therefore, suggestions for further research are to have more in-depth significant experience with enough time to get more data to support this research to provide stronger and meaningful descriptions of the implementation of a retest to improve students' academic achievement.