Ask his teachers which high schools they recommend for him.And talk to him about setting goals to get in: do all your home, work for A's, sign up an academic summer school program, take a test prep class in Fall of 8th grade.
Here's a list of specialty programs.
http://www1.pgcps.org/aboutpgcps/index.aspx?id=172037
Besides science and tech at Roosevelt, my kids' teachers recommended the high school program at PG Community College, and maybe the p RT orgasm at Suitland. I was surprised they didn't know much about the visual arts program at Northwestern. I know some kids there who like it.