Filtering the data displayed in a list

Hi all,

I'd appreciate some guidance in the right way to filter the data
displayed in a list. I have two models, school and centre (centre
belongs_to school and school has_many centres). In the list action for
centres at the moment it shows all of the centres for all of the
schools. I would like to be able to add links on the page to allow the
user to choose either all centres (as at present) or just the centres
for a particular school. I have in mind links for "All centres | North

South | East | West". I'd like to keep the result in the current

page so if there is a way to have the default to retrieve all centres
and the other links to retrieve the centres for the North, South, East
and West schools respectively that would do nicely.

I have put the relevant pieces of code for the centres controller and
the list view for centres (and happy to provide other code on
request). I could probably hack this to get a result but I'd really
like to understand the right way to do it.

Anyway, any help will be much appreciated.