The aim of the study is to examine assessment experiences and practices in mathematics in high school from the students' perspective. To gain insight into the students' experiences and practices, we used a qualitative approach. The data are based on qualitative focus group interviews with first year students in the general studies education programme. The findings show that the students mostly receive summative feedback on achievements which is expressed through grades. To varying degrees, the students seek feedback during the learning processes, thereby leading to differences in the amount and type of feedback that the students receive as well as the extent to which feedback improves learning and outcomes for all students. The students' perceived usefulness and active use of feedback is mediated through the teacher's manner which also influences motivation and effort. The study shows a potential for involving students in assessment and using feedback during a learning process as a significant tool to promote mathematics achievement.