How do I use a dropdown list based on multiple nodes data that will display a list?

Yep that is a pretty long question. So let break it down for you (and I).

How do I use a dropdown list based on multiple nodes data that will display a list?

I have used flexinode to create custom nodes and it is working great. The node goes like this:

School
-Logo
-Teachers
-Description
-Web site
-Location
-Etc

I would like to create a page that has a dropdown list witch contain all "location" possibilities. When I use one of the location, all school teaser in this place (or city) will show.

For exemple, I have 4 schools. Locations are Laval, London, New York, and Laval.
The dropdown list will contain Laval, London, New York. If I choose Laval, two schools will show in a list.

Thanks for your help!