If a Master has the right to teach his disciples, it is because he has worked at his own perfection for years and years during many previous incarnations. The day will come when you too will be able to instruct disciples.
When? When you have attained self-mastery and succeeded in overcoming all your weaknesses. In the meantime, do all you can to improve yourself so as to have the best influence possible on all those with whom you associate.
This applies not only to teachers, professors, parents and educators; it applies also to all employers, to everyone in a position of responsibility.