Personally while I get the desire to 'educate' them as to the WHY cause if gives you vindication and justification and well closure IME it generally leads to a nasty escalated conflict over the termination as the client already feels stressed having been 'terminated' to have all the reasons lined up in writing just adds insult to that injury and makes them want to be defensive back and than this back and forth of you do this and that occurs.

If you are giving notice where you have to SEE these people day in and day out I would keep it short and sweet ... bottom line they are no longer a match for the program and that final decision is YOURS to make you want them to leave as quickly and peacefully from your program as possible .... they are no longer your problem to FIX so do not even try - their role is to reflect on issues that have arisen during your relations and figure out why this happened to them and hopefully learn and be more respectful in the future relationships they have