This paper reports on the washback effects of Malaysia's School-Based Assessment (SBA) on Form 4 students after almost a decade of its implementation in the country. It critically examines how SBA has affected Form 4 students' overall perceptions about the learning of the English language at school. This study also investigates the challenges that the students are facing with SBA in their school. In this sequential explanatory study, the data were collected via three methods: questionnaires, interviews, and classroom observations. It was found that there was a presence of positive washback in the students' perceptions of and attitudes towards SBA. Themes, such as engaging activities and constructive feedback, emerged, which showed the students' positive perceptions of SBA. However, the major challenge that the students were facing was with regard to the availability of the right resources at school for SBA. The findings of this study contribute to a better understanding of the status quo of the phenomenon of SBA and its impact on language learning and teaching in the context of secondary schools in Malaysia.