Dress to the Level of the Job Environment
Teachers are exemplars to the young people they teach. The way you dress sets an example just as your speech patterns do. That being said, it makes a great deal of sense to dress conservatively when you interview for a teaching position.
The standard classic prep look is always acceptable in private school circles. A blue or white oxford cloth button-down shirt paired with an old school tie or rep pattern is understated and elegant. Add khaki or grey slacks to that together with black socks and a slip-on loafer style shoe and you are all set. If you wear bowties, then do so. Not the big floppy kind, but instead a conservative one in a rep pattern will make the right statement. A blue blazer is appropriate in cooler parts of the country. As a rule you should wear your jacket and only remove it if invited to do so. Your hair should be neat and trimmed.
Now, if at this point you are complaining that you will look like the headmaster, that's the point. You want to dress at least one level above the position for which you are applying. How will the person who is interviewing you be dressed? Take your lead from him or her.
What about religious garb? If you wear a yamulka or a turban as part of your daily routine, there is no need to change that.
What Doesn't Work
A fashionista look of any kind will most likely raise eyebrows. So will a bold hair style like a mohawk or a mullet. If you are bald, accept that fact and resist the David Gergen style combover, or just as nasty, a bad hairpiece. Also verboten are dye jobs, diamond pinky rings, Rolex watches and other ostentatious accoutrements. Save them for another non-critical occasion where an impression doesn't matter. Don't wear after shave or cologne. Your body language is important too. Sit tall. Be alert.
A classic look suitable for any professional, semi-formal setting is acceptable. If you have a large bosom, manage your decoltage so that it is not the center of attention. A jacket over a blouse paired with a skirt or pants makes the right impression, assuming, of course, you select conservative colors. Comfortable shoes can be flat or with a short heel. Stop and think what the person who is interviewing you will be wearing. Follow suit.
Keep the makeup, perfume and jewelry toned down. This is not a night on the town. It's a job interview.
What about religious garb? If your religion requires you to wear a headcovering or a burka, then do so.
What Doesn't Work
Loud colors, short or tight skirts, heavy makeup, excessive perfume and body language which screams "I'm sexy" are not appropriate for a job interview. Nor is the opposite appropriate either. There is no need to dress like your 80 year old aunt Mildred.
Get a Second Opinion
It never hurts to have a trusted friend, preferably an older friend, pass judgement on your interview attire. He or she will spot things you may have missed. That second set of eyes could make all the difference between success or failure at your teaching job interview.
Look at the School's Website
You probably have been looking at the school's website anyway. But circle back and look carefully at all the pictures of the staff. How are they dressed in the classroom? If you have a friend who already teaches at the school, ask her for advice on how to present yourself.
Now relax! After all this careful preparation you will do fine.