Also last Saturday, police in Greensboro, North Carolina, reported that a four-year-old boy who found a loaded .38 calibre semi-automatic in a handbag had shot dead Carlos Gilmer, a six-year-old playmate who had been celebrating his birthday.
Following the death of the teacher, Andrew Wurst, 14, a middle school student from Pennsylvania was charged as an adult with murder, assault, endangerment and gun and drug charges. He was carrying a small amount of marijuana when he was arrested.
About 240 students were attending the dance when Andrew Wurst allegedly walked in and fired several shots from a handgun.
Science teacher John Gillette, a 48-year-old father of three, was killed. Two 14-year-old boys were wounded and treated at a hospital and a female teacher was grazed by a bullet but not seriously hurt.
As students ran for cover, several hiding in a closet, the owner of the private function hall where the dance was held chased Andrew Wurst with a shotgun and caught him in a nearby field.
Classmates said he had promised he was going to make the dance "memorable" but he made no specific threats and they did not take him seriously.
"He had a really sick sense of humour," said one friend. "He would laugh when he said it: 'I'm going to go to the dinner dance and kill some people'."
Other pupils said that Andrew Wurst had told them he wanted to kill people and commit suicide.
They said Wurst was a fan of rocker Marilyn Manson and his dark music, was unhappy at home and had become obsessive about girls.
The incident follows separate fatal school shootings in Mississippi in October, in Kentucky and Arkansas in December and again in Arkansas in March.
The death toll now is 12 killed and 25 wounded. Before the Pennsylvania shooting, President Clinton has ordered a nationwide investigation of the schoolyard killings.