"Which" or "What"

[Mormor]

I'm helping a Chinese woman improve her English. Is there an easy-to-understand rule governing the usage of "which" and "what"? For example, which of the following sentences is correct and why:
1) Which school do you attend?
2) What school do you attend?

Can anyone help? Mormor

 

[David L.]

In general
'what' is used when you are seeking information, plain and simple.
'which' is used when you are asking for information and there is a specified number of people or things from a definite set to choose from.

'What school do you go to?' is seeking the name of the school he attends.

compare

'You come from Smallville! As I remember, they only have two schools. Which school did you go to?"