Why do teachers make such a large impact?

In my APUSH course, we're doing a project on who you would nominate to be in an American History Hall of Fame. Each pair had to choose five individuals to be nominated for the Hall of Fame. For our final nomination, we decided to use our instructor. After a page displaying a photo of them with their birthdate, etc., on a second page, a small biography of them, and why they are nominated is displayed. At the top, the area what shows why they are nominated, is going to have a small thing on how teachers make a giant impact in the life of their students, forming and molding them into model citizens, etc. Why do teachers make such a large impact? What is it that they do, that inspires students? Any responses are greatly appreciated.