In the 1960s there was a popular garment called a muu-muu. This shapeless dress, adapted from the Hawaiian islanders, was designed for maximum air circulation. Arabs keep cool in the desert by draping themselves in loose robes from head to toe.
Some teachers, according to contributors to The TES online staffroom, meanwhile, believe they need to expose copious amounts of bare skin, and possibly bits of thong, in order to fight the roasting English temperatures (see page 1).
We say go ahead - once you have decided you will feel comfortable about the comments your pupils will make behind your backs, refreshed your memories about what teenage boys are like, and thought about whether there needs to be some "distance" between children and teachers. But don't pretend it's to keep cool rather than to look cool.