(CNN) - Seniors at Kenowa Hills High School in western Michigan thought organizing a mass bike ride to school was a sweet sendoff for the last day. They even got their parents, police and the mayor on board.
But not the principal - she sent dozens of students home and banned them from last-day traditions after the ride this week. Now, parents and students are protesting her response.
Police escorted the 100-person bike ride, and parents lined the route. The Walker, Michigan, mayor brought doughnuts. But principal Katharine Pennington sent more than 60 students home, CNN affiliate WOOD-TV reported, because she said the ride was dangerous, tied up traffic and prevented staff from making it to school.
The school has a zero-tolerance policy for senior pranks, students and parents told CNN.
Soon-to-be graduates were banned from participating in the senior walk - a traditional final walk through the school's hallways - and some were told they wouldn't be allowed to walk at graduation, a decision that was later reversed. Students told CNN today the senior walk was rescheduled, too.
"She had absolutely no clue, but, I mean, that was the whole point of it," Kenowa Hills senior Cody Nicks told CNN. "It wasn't even a prank, but a celebration for our last day ... The way it was reacted to was completely absurd."
The principal's response to the ride, which was held during National Bike Month, sparked protests among parents and students. So many packed a school board work session Tuesday night that they moved the meeting to a middle school auditorium, WOOD-TV reported.
Pennington did not return CNN's calls.
"Most of us senior parents did know about it. We found it harmless," Cody's mom, Rachel Nicks, said. "They wore bright colors, police escort ... I don't know how much safer it would have been if they would have notified the administrator."