I am left wondering if indeed you are a lecturer in a university or so. You must be very weak for students to dare do all those tricks on you so that you can dish some free marks. Probably they have noticed that you are of that ilk. I can tell you that weak students tend to stay away from strong lecturers, even physically running away from a lecturer's path.
My own simple advice to you is to respect your work and be serious with it and everything else will fall in place, that is if you are bothered by the students' antics.