In this study, it was investigated if student feedback promoted teachers' insight into where they could improve their lessons and their reflection on their lessons. It was also studied in what ways teachers worked on improvement, based on the student feedback, and whether it affected the quality of their teaching. Student perceptions of teaching quality were measured by means of a smartphone application for providing teachers with feedback on their lesson. Teachers in this study (N = 60) were randomly assigned to the control or experimental group. The smartphone application was used several times by teachers to obtain student feedback. The teachers reported that they gained insight into where they could improve their lessons. They reported improvement-oriented actions in response to the student feedback. According to students, teachers first slightly improved their teaching quality. However, teachers did not seem to reflect significantly more on their lessons and their improvement did not sustain. Explanations for the findings are discussed and suggestions for future research are presented.