Students at La Porte High School were dismissed early Tuesday after water started gushing out of a failed sprinkler head that set off the fire alarms.
About 10:30 a.m., the close to 2,000 student body was evacuated when the alarm triggered a response from firefighters who quickly discovered there was no fire.
A sprinkler head in the boiler room toward the south end of the school failed, sending a cascade of water onto a transformer that distributes electricity to the indoor swimming pool, said LaPorte Schools Superintendent Rande Thorpe.
Thorpe said the students were sent home about noon because there was no fire protection when a large portion of the sprinkler system was inoperative to fix the broken head.
The repairs were expected to be completed by late afternoon and he expected school to resume Wednesday.
"The students were always safe at all times. They were not in the area of the sprinkler head and transformer," he said.