In any curriculum or course that teaches or emphasises the, use of modelling, a critical concern is evaluating the modelling artefacts that students produce, leading to the production of feedback. Students need to be able to use this feedback to improve their understanding and to become better, more mature modellers. In this position paper, we discuss the challenges and importance of evaluating modelling (and related) artefacts and providing precise and reproducible feedback. We also discuss some possible principles and criteria for supporting this critical part of how we teach modelling.