Dena,
There really is no "decision", per se. Your obligation is to make reasonable accommodations for him within your program. If you aren't sure what "reasonable" is in this particular instance, I'd be glad to discuss it with you (JaneJarrow@aol.com). But the fact that it was not discussed with him in advance doesn't mean that he isn't aware of the way the field is typically carried out. It would have been better if it had been discussed up front and your concerns for his future were expressed, but neither have you made promises to him. It is never too late to sit down and have a frank discussion.
Dr. Jane Jarrow