During Roger Waters's epic The Wall show at Verizon Center last night, a children's chorus came out to sing during "Another Brick in the Wall." Well, those kids were from West Baltimore, and they're in the BSO's OrchKids music program. It must have been quite a blast, going from Lockerman-Bundy Elementary to being onstage in one of the biggest rock spectacles of all-time. "It was insane," says OrchKids director Dan Trahey. "The kids killed it!"