Teachers, whether or not they realize it, have an extremely powerful influence over their students. Students look up to instructors more than to just teach them from textbooks.
Teachers have the power to change students' lives and their way of thinking.
Some times, teachers have greater influence on their students than the students' parents do. The students represent the future, and their way of thinking will shape the world. The leaders of today will retire or pass away, and they will not have much say in the world's politics. The students will be the ones to regenerate and sustain the human population, and, hopefully, the environment. Without protecting the environment, the human population will cease to exist.