In the student performance statistics, there is a special qualitative indicator that records and compares your students’ progress before and after feedback. When sending assignments as part of feedback, it is recommended that you indicate them as Feedback when sending them. In this way, you gain the ability to draw useful conclusions about the effectiveness of your teaching work in general. Click on the Statistics 
icon in the book you are teaching within the course. Click on Advanced View and focus on the indicator with the number 22 (see explanation table ?).