My research is focused on developing e-learning systems that provide high-quality feedback on student submitted programming exercises. To create such systems we use a new approach of applying case-based reasoning (CBR) techniques which proved to be successful in other areas such as technical support departments and financial institutions. The increased quality of feedback delivered by our system will help to keep students engaged, which in turn will reduce attrition rates. A prototype system has been tested in several undergraduate Computer Science courses with promising preliminary results. The effectiveness of the completed system will be thoroughly evaluated in CS classrooms.