A school teacher injured his back and had to wear

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. When a strong breeze made his tie flap, he took the desk stapler and stapled the tie to his chest. Discipline was not a problem from that day forth!