One key, I believe, to effective teaching is realizing the eternal impact that you are making. When you are doing the same thing week after week, you don't always see the immediate effects. If you are a teacher, one thing is certain, you are making an eternal impact for better or for worse.
Even more important than what a person teaches or says, is the example she is setting for her students. One does not often realize how she is influencing those under her. There are many people in my life who have influenced me, as I am sure the same is with you. Most of those people probably have little or no idea of the impact of their influence. The Bible calls us sheep. We look up to those we admire and often follow their example. Right or wrong, I have often found myself saying, "well this person does it, so it must be ok."
While students should be looking to Christ, the ultimate example, you cannot escape the fact that they are looking at you, their teacher. God will hold you responsible for the example that you set. It is easy to say, "well, I'll just give in to this sin one time. It won't matter." The truth is that one wrong choice does matter. Just consider the wrong choice that Abraham made thousands of years ago. Who would have known the impact on the entire world by just one wrong act?
Just remember that you are influencing eternal souls. You are influencing the choices that will be made by your students for the rest of their lives. God will hold you responsible and you will be called in to account for the example you have set. The choice is yours - what example will you be?