Wireless Password as Part of Image

We have moved from an open wireless network to a protected wireless network, and are experimenting with sending out the network name and password with the base OS image. When the image is deployed to a Student Mac Book, it keeps the name and password under Network Settings as a Preferred Network, but does not automatically connect to it without the user choosing to select it. With the open wireless, we connected to it, made the OS image with that Mac Book, and when deployed, all Mac Books with that image connected to the open network without user intervention. We can't seem to make it work with the protected wireless, though. Any suggestions?
Tom Queck
New Kensington Arnold School District