Chris,
Here are a few additional thoughts on the matter of moving to an OSS based solution for your school district.
To begin with, when it comes to cost, Microsoft makes it very easy for an educational institution to stay with their software. Open Licensing for Education can get schools a copy of Exchange 2007 enterprise for less than $500; CALS for server or Exchange run around $30 each; Office costs about $30 to $50 per license. Of course, the more an organization buys, the cheaper the pricing. Software assurance also provides some built in technical support offerings and upgrade protection.
I mention these prices, assuming open licensing for education, for a couple of reasons. First, there is a large existing ecosystem of applications, support, and trained and certified support people who are used to installing, managing, and working with software in the Microsoft ecosystem. The functionality and suggested applications of Microsoft products is well documented, and because of the large support and compatibility infrastructure, quantified and certified help is easy to find. Many of the other products available in the Microsoft ecosystem are also well documented and well tested. In addition, a large majority of the user population is familiar with the operation and utilization of products built upon the Microsoft ecosystem.
Second, because of the free form and open nature of the open source software environment, there is no unified development API, no unified support structure and few documented and certified support people. In order to get these kinds of assurances of functionality, support, and compatibility, it often means moving to one of the big open source product and service providers that offer proprietary addons and professional level support services. Firms such as Red Hat, Novell, Canonical, Sun, Xandros, and Mandriva come to mind. The professional level educational priced offerings that these companies offer are in the same price range as Microsoft's open education licensing. In addition, since most of the computer technicians in the USA are Microsoft centric, an organization may need to spend additional dollars in the first few years, and when staff changes, to get the level of functionality needed because the staff are not as familiar with the open source or *nix based solution as they are with the Microsoft based offering.
In addition, as the architect of a school system's IT system, you need to think about what happens to the network if you leave/die/quit. Will the next hire be able to continue operations? Will that person have the necessary skills to navigate a wide-ranging and disparate OSS system that may not be completely documented? These are important things to think about.
I have seen two school corporations in a rural midwest state have trouble because their OSS guru technical staff person left. When the corporations went to replace these people, they could only afford someone with Microsoft skills, and in the end, those organizations lost data, functionality, and time re-creating the network infrastructure because the OSS networks had been pieced together out of various free offerings that did not have business level support, assured compatibility, or professional grade documentation. The Microsoft centric replacements, who were the only available replacements for the money in the budget, couldn't make heads or tails of the hodge podge of services, scripts, and other assembled disparate parts that the OSS gurus had been able to assemble in to a working whole.
