Oh, come on! A Thong?
That is ridiculous - there is a clear difference between how professionals dress for work, and how the average person dresses. Professionals do NOT flaunt themselves in revealing clothing. They dress on the formal side.
Furthermore, a teacher in body-revealing clothing is laying (entendre intended) themselves open for a sexual harassment suit by co-workers and students.
In any hierarchy, there needs to be a division, which generally is marked by clothing/uniform differences, between the officers and the troops. In a sense, in a school, the kids are "the troops" - those that take orders, and follow the teacher's direction.