We have exam accounts similar to others where we have them inactive until the session requires them, teachers manage which student uses which account and we just administer the accounts themselves, taking a backup after the exam and putting that in a secure area for exams staff to access. We then clear and reset the accounts using AD Manager. We have headaches with them though and I would like a better solution if anyone can suggest something else they do as the logistics of it all can get a bit overwhelming.