Teachers should provide informed and impartial critiques immediately after the exercises. This quickly becomes a resource problem. Part of my solution has been to make extensive use of practitioners and student peer evaluators. There are many collateral benefits to this beyond the availability of evaluators. I train these evaluators in the techniques of the critique method, although time for training is always at a premium.
Training is essential because critique is a powerful learning tool.
If used inexpertly, it can do more harm than good. I also train students, whose work will be critiqued, about techniques they can use to maximize the learning experience. Again, time restraints are a limitation. However, its success depends on whether the critique helps the students to understand how they need to improve and encourages them to do so. This learning method demands hard work by faculty and students alike in the form of thorough preparation and diligent application.