Besides the obvious reasons for evaluating student work (e.g. for the administration, for an accrediting agency, because a grading system exists, etc.), the primary reason for doing so is because it can aid student learning, and serve as a useful teaching guide.
To be most effective as a teaching and learning too, the evaluation of student work should meet the following criteria:
1. Evaluation of student work is clearly connected to learning goals, which are outlined in the course syllabus.
2. Evaluation techniques are measuring those learning goals.
3. Criteria for evaluation are clearly stated, either on the syllabus or on a project information sheet.
4. Student work is being evaluated against those criteria.
5. The results of the evaluation are being fed back into student learning and into teaching methods for that course.