Allowing faculty members and students to bring their laptops to school is the most cost effective way to get to 1 to 1. In most districts this is not an option. There is concerns about management of the laptops, virus and botnet attacks as well as network intrusions.
While these are all very valid concerns I believe that they can be addressed through infrastructure configurations. There are both old and new technologies that can control client access on a network which would eliminate most of these concerns. We have been successful in our district by making some minor configurations and an investment in infrastructure.
We implemented a managed wireless network. These networks are available from Cisco, Meru, Aruba, Trapese, Ruckus, and a few other. This type of network allows all of the access ponts to be managed by a controller. ON this wireless network we broadcast two SSID (these are the names of the wireless networks that the computers can see and connect to). One is for internal users (our school owned computers) and the other is for guests.
We segment our network in virtual lans (vlans). What that means in simple terms it that each network port is assigned to a group. Each group has different access and rights. This allows the students to not interrupt the admin network for example.
On our wireless network we assigned the SSID Guest to the Vlan Guest. By configuring Access Rules in our switches we have limited the guest account to only have access to the internet. They can not access anything else on the network. If a student brings in a laptop with a virus the virus is contained to that machine only. Because of the access rules and the vlans the virus cannot access any of our servers. This is how we allow teachers and students who bring their own laptops in to connect.
With all of the amazing web2.0 sites and tools available access to the internet only really does not limit what the student and teacher can accomplish. A $400 netbook and the guest internet access can go a long way.
In our network we have a Cisco 4507R Core Switch and HP Procurve switches at the access level. We have a vlan for admins, teachers, student, printers, computer lab, wifi and wifi guests. We use a MERU ABGN wireless network.
Please remember that the more computers you have accessing the internet the more bandwidth you will need. If you are concerned about students managing files you need to look into a web based classroom management solution. Moodle or schoolwires are two examples. Flash drives are also a good option.
This is a simple explanation of how to setup your network. It should be designed by an IT professional. Just realize that most of these technologies already exist on your network. The required investment in infrastructure is significantly less then purchasing a laptop for every student.