One nationwide program is administered through Johns Hopkins University. It can help identify strengths in young students and offers various classes both online and in person. Some school districts coordinate with JHU in administering certain tests. The web site is below.
Best of luck!
Recognize, too, that there are varying levels or degrees of GT programs. Some are on a class-by-class basis. Others are total immersion--if a kid qualifies, he/she attends only GT classes.