To be hired by the FAA now you must attend a CTI program. CTI stands for Controller Training Initiative. You are correct that there are 13 such schools across the nation. Three that come to mind are Beaver County Communitity College, University of North Dakota, and Embry-Riddle in Daytona Beach, FL. I attended ERAU Daytona and majored in aeronautical science but minored in ATC. I really enjoyed the experience, and was ready to pursue a career in ATC had I not gotten the flying job (my true love) that I currently have.
Here is a map with links to the 13 schools:
http://www.faa.gov/careers/employment/AF-CTI-MAP.htm