A CMS for School Districts

I’m soliciting all you geeks out there for some recommendations. Currently our school division website is using Mambo as it’s CMS. It certainly has a lot of great features and components. As a new division we’re hoping to use one CMS and create 45 school websites using a single instance of the CMS rather than having separate installs for each school.

We’d be happy to stick with Mambo but need something that’s quite simple for end users to use. Mambo is fairly complicated from the back end.  Does anyone have a suggestion for a CMS that would allow us to use a single installation of a CMS and create individuals websites off of that? The template would be similar but ideally it would be great if each school had some control over the navigation and css.

So all you geeks out there…what do you suggest?