How can teachers prevent students from being bored in their class?

Do your work, its the simplest answer other than waiting for time to pass by and proceed home.

Answer

Watch the clock and watch it go until the bell rings.

Answer

Keep Word puzzles such as crossWords, cryptics, Diffney's, etc on hand. You can try to keep them related to your subject and possibly offer extra credit points

AnswerPlay rock paper scissors with yourself and accuse your left hand of cheating