David,
Being honest and upfront about the challenges students may face, based on your observation of their performance in classes (with, as you suggest, all appropriate accommodations in place) is never a problem in my mind. The problem only comes when the "you probably can't be successful in this field" discussion comes before the student ever enters the program, before you have seen the student in action, and before the student has an opportunity to show what he/she can do. Being honest about what you see is good teaching. "Being honest" about assumptions (which are generally based on stereotypes) is… >>>