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-alecky punks, having already heard the new teacher was a former Marine, were leery
of him and decided to see how tough he really was, before trying any pranks. Walking confidently
into the rowdy classroom, the new teacher opened the window wide and sat down at his desk.

When a strong breeze made his tie flap, he picked up a stapler and promptly stapled the tie to his chest.

Dead silence. He had no trouble with discipline that year.