NEW LONDON, Texas — On March 18, 1937, a natural gas leak beneath the New London School rocked the ground with a deafening explosion. It sent the floor up, chunks of concrete flew dozens of feet into the air, and then the roof caved in, burying both students and teachers alike.

When the smoke cleared, 294 people lay dead. The final bell was to ring only minutes before the explosion. 

The explosion took place the day before Christus Trinity Mother Frances was set to open and have its dedication. However, those plans were quickly scrapped as the injured and dying were taken to the hospital for care.

The tragedy remains one of the deadliest school events in American history.

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It took about 40 years for the community to open up about the tragedy.

"Daddy would not say one word about the school explosion," John Davidson, whose sister was killed in the explosion, said. 

Davidson says he did not really understand what happened until high school. 

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"We'd walk by the center of town every day," Davidson said, "I read the names on it [the memorial] but it didn't dawn on me until high school just what happened here."

At the museum Davidson showed CBS19 a picture of the softball team. 

It was taken just hours before the blast. He points out the students in the picture that died that day. One of them was his sister that he never got to meet.

"Mother would say a few things, tell me about teaching Ardyth to drive, how pretty she was," Davidson remembered. 

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Many of the victims identified by what they were wearing to school that day, or an item they always had with them. Authorities identified others when school started back up and no one responded to that name during role call.

Bill Thompson was a survivor of the explosion. He switched seats to sit by his friend. 

When he went back to school and heard the name of the student that he traded places with, he found out she died. He says he still cannot get passed the guilt.

"Our daddies and mothers, as well as the teachers want to know that when we leave our homes in the morning to go to school that we will come out safe when our lessons are over," Carolyn Jones, the tragedy's youngest survivor said in a video that plays at the museum. 

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At the age of nine, Jones went to the Texas Legislature to plea for something positive to come out of the disaster so the deaths of her classmates would not be in vain.

"Right after her plea that day they passed a law that put the odor in the natural gas. A man-made chemical called mercaptan," Davidson explained. 

The Engineering Registration Act was also passed. It established a board that would license people as engineers.