a student in a physically demanding training course (like automobile driving) who shows up with one or more major disabilities (for example, untreated Tourette's Syndrome, absence of all but one
finger on one or both hands, IQ of 60 or below, cerebral palsy, other profound physical or mental disabilities) which went unmentioned by student's
parents because they didn't want the student to be treated "differently from the other
kids."
"Woops. We have a stealth student over there... Mom and
Dad forgot to mention that he's a
high-level quadriplegic when signing him up for defensive driving over the
phone."