Your problem is rooted in your perception of the people in front of you. You consider them to be your judges. In fact you transfer the inner archetype of your father on them, so all of them represent your father who can say whether your performance is good or not. You had quite a strict father, didn't you? ;)
There are many ways to overcome that complex of yours. I can recommend special trainings of assertiveness if you can find any where you live. But even without that you can start by visualizing the audience as funny small rabbits (just imagine their long ears! :) or silly 5 year old kids. Or you could even visualize them all naked That may sound funny but it helps. The trick is to make yourself the main judge of what you do. The audience is there just to hang on your every word with their funny long ears
Turn it into fun and you will gain confidence.
- For Teachers