Fortunately I work in a school where there is no dress code. This is important because we are a playful school with a great big grassy playground. Mostly, to teach well, requires playful clothes that allow you to sit on the floor with a group of children, explore outside no matter what the weather is, and move a lot as we teach and learn each other.
Sometimes, however, the day may warrant fancier clothes and shoes or perhaps the mood you want to create or lessons you want to present profit from a dressier look.
In general, I believe there should be no dress codes at schools and people should wear the kinds of clothes that allow them to teach well in all kinds of circumstances. Onward.