A group of children as young as 7 in the small Pennsylvania community of York Haven taught each other to have sex, and half a dozen of them have been charged in juvenile court. The children hid their activities from adults but readily answered questions asked by police. Six children have been charged in juvenile court on charges including rape, involuntary deviate sexual intercourse and indecent assault, police said. At least one has been convicted and sent to juvenile detention facilities. Incidents of incest were discovered but not pursued criminally, police said. No adults were charged, and the case is closed. The activity started 2 1/2 years ago with a few children, and by the time authorities learned of it in December, 17 youngsters ages 7 to 16 were involved, police said.