Listen first - Apply Consequences Later
I am an administrator at an adult career college. The program I administer is rigorous and has very high expectations for student learning. Usually when the students in my program are stressed it manifests itself in attacks against teachers or polices.
I have found that just calling the student into my office and saying something like: "Wow, you seem really unhappy/stressed out/frustrated/etc - tell me what's up" is the most often the key to resolving the problem.
If you sit and listen, ask questions for clarification,validate their feelings and let them know that you want them to get the best education possible - that alone is often the solution rather than changing policies or faculty methods. Once they feel heard and know that you care about them, much of the hypercritical "noise" goes away.