The manner in which a woman teacher dresses is extremely important, as is self-understood. This is so not only in the upper grades, but in the lower grades as well.

One should be extremely mindful of this matter. Especially in light of the tale that in the Tzemach Tzedek's times a Shochet was removed from his post because he wore galoshes. Surely there is no prohibition against wearing galoshes. However, it served as an external sign and manifestation of that which was transpiring inwardly.

And a word to the wise is sufficient.

Excerpt from Igros Kodesh, Vol. IX, p. 216