This study examines mathematics teachers' assessment practices for senior high school students in Ghana. Formative assessment has been identified in the literature as having a significant impact on students' learning. However, less attention has been given to students' perceptions of teachers' assessment practices in Ghana. Data involved questionnaires for 420 senior high school students and 308 senior high school teachers in the Ashanti Region of Ghana. The results showed that students and teachers hold different perceptions of assessment practices, and suggest teachers should pay more attention to questions, homework, student observation, student demonstration and group work to support students' progress and better examination attainment.