Help needed - Computer Driven P.A. System

I want to build a P.A./Break Time bell system for my local school. I want to control it from a PC. At certain times of the day it should generate some form of alarm (wav file) to advise of a break or dinner time. I can write the software to control it, but do not have a clue as to the electronics needed. Would I use a normal sound card attached to an external amplifier, or would I need something special? Any help on this would be appreciated.

Thanks

Yes, the soundcard output can drive the PA. But keep in mind: Windows also generated different tones itself,disable it.

This must be a science project - to see if you can do it. Otherwise, it makes no sense to drive the PA with a $1000 computer in place of a $50 switch. Hope you get an A.

he needs a Wav file ...
but might use a recorder chip too.
but it seems like a practical idea.
but instead of a compuster you can use a cd player.
but the reason for the computer is that he needs to make a program ro play the file automaticly at some preset times wirght?

just feed the output of the soundcard into a 100v line pa system this will allow you to feed the speakers in the school with the signal and will only require bell wire between the amplifier and speakers