Avoid provocative, tight, or skimpy clothing at school. This is true for male teachers as well as female. Guys have it easier than ladies here. A nice pair of pants, button-front shirt, and tie CAN'T go wrong. A nice sweater works too.
Jackets are optional but look great for conferences, open houses, and meetings.
The toughest rule for guys is to have a nice pair of shoes and a good belt . Great clothes with cheap or dirty accessories just won't work. Own one or two nice pieces of jewelry. We don't have to be rich. Test clothing for classroom readiness before you leave the house.