Vandals let the air out of the front tyres of all 22 big yellow school buses in the education district of Ridgefield, in Washington, forcing administrators to call on neighbouring districts for help.
Bus drivers finished delivering their own pupils before making their way to Ridgefield to rescue its 2,100 stranded pupils.
In the end, the vandals' hard work resulted in only a two-hour delay to the start of classes.
School staff were frustrated: "We're all in crunch time, trying to get everything done. The last day of school is June 11, so missing almost a day like this is tough on all of us," said Debbie Adams, a teacher.
"I was thinking, senior prank."
But Art Edgerly, the school district superintendent, said he had never heard of such a prank before.
"It's not a tradition of any kind that I know of," he said.