I agree that with students the first impression is a lasting impression. My opinion, students start observing you most of the time before you walk into the class room. When a student discovers that they have a certain instructor for a class, they start asking other students who you are and what do they think of that instructor? Now the student have a preceed idea about you. It is now in your hands to make a positive impression if they have the opposite idea of your knowledge and skills.
