Where would you like to be in your career five years from now?

A genuine answer is perfectly acceptable. The needs of the school differ from one school to the next. Use your best judgment and look into teacher turnover rates. If they are high, the school is most likely looking for someone who will stay for 3 years or more. An appropriate answer will depend on your level of experience. If you are new, it's often best to show a moderate level of ambition tempered with patience.
It is most important to demonstrate that you're stable and resilient and that you're willing to put the school's needs ahead of your own.