Teachers dress like slobs. Another discipline problem. Teachers will show to class wearing seat pants and t-shirts. When I went to school, teachers dressed professionally. There are ways to dress comfortably and still look professional.
Image means a lot to a child.
Children pick up on visual cues. Again, they are sponges. Give them a positive image and they will learn that it is a good thing. Show them slop and negatives and they will think those are good and appropriate things. Teach children that learning is fun and necessary.