No problems A former Sergeant , having served his time with the Marine Corps, took a new job as a school teacher, but just before the school year started he injured his back. He was required to wear a plaster cast around the upper part of his body. Fortunately, the cast fit under his shirt and wasn't noticeable. On the first day of class, he found himself assigned to the toughest students in the school. The smart-alec punks, having already heard the new teacher was a former Marine, were leery of…