CTI school is only meant to cover the first six weeks of FAA training, which is done at the FAA ATC Academy in Oklahoma City. After completing CTI or shortly before finishing, you have to take the AT-SAT, for which you'd be prepared by a CTI school. After that's done, you have to wait for an invitation to the academy. The latter step has taken between 1 and 3 years after CTI graduation to happen. Yes, this means you'll have more training after completing CTI. Then you are placed in a facility and have to go through their training program as well.