"Discipline in class" joke

A school teacher injured his back and had to wear a
plaster cast around the upper part of his body. It fit
under his shirt and was not noticeable at all. On the
first day of the term, still with the cast under his
shirt, he found himself assigned to the toughest
students in school.
Walking confidently into the rowdy classroom, he
opened the window as wide as possible and then busied
himself with desk work. The classroom became a bit
unruly and he admonished them.
This happened several times. When he could do work at
his desk, the strong breeze from the window made his
tie flap annoyingly. He kept rearranging and
rearranging the tie as the class raised its level of
unruliness.
Finally, becoming disgusted with the wayward tie, he
stood up and took a big stapler off his desk and
stapled the tie to his chest in several places.
Discipline was not a problem from that day forth.