Hi for starters, read up on the school and its system, ie the curriculum, profile of the students and teachers. They should have a website?
Don't worry about being an older teacher cos even in government schools here, teachers are getting increasingly older. Unlike in the past where most if not all teachers joined the profession straight out of school, many now go into teaching after having worked at other jobs for a number of years. What you have to offer includes maturity and experience, which a young graduate may not necessarily have.
Err on the side of caution and dress conservatively. If it's not feasible for you to wear a smart jacket to the interview cos of the crazy weather, bring one along with you and put it on before you proceed to the interview. Smile and project confidence but not cockiness.
Good Luck!!
