Courtesy Rachel Nicks

The Michigan high school principal who faced blistering criticism after she suspended scores of graduating students because they staged a bicycle-riding parade to school as a senior surprise has issued an apology for her actions.

Katharine Pennington, the principal at Kenowa Hills High School in Walker, Mich., was dismayed at not having been informed in advance about the students' planned bike ride.  When the estimated 60 students arrived at school on Tuesday morning - the final day of their senior year - Pennington suspended them for the day, forbade them from participating the day's annual senior walk, and even suggested they would possibly not be able to walk at their graduation ceremony next week.

In audio of the principal's reaction recorded on one student's cell phone, Pennington could be heard taking the students to task for what they had done:  "That's it. The short and sweet: Call and get your butts home. You're not participating in senior walk today. If you and your parents don't have sense enough to know your brains could end up splattered on Three Mile and Kinney, Fruit Ridge, then maybe that's my responsibility."

But the students had notified police beforehand. A police officer in a cruiser and city of Walker Mayor Rob VerHeulen were present during the procession.

Pennington said the ride tied up traffic in the area, put the students in danger and caused school staffers to be late for work.

In her written apology today, Pennington acknowledged her error.

"Yesterday, I made a mistake and sincerely regret my actions. Did I overreact? In retrospect, of course I did. My first response to learning of our high school seniors riding bikes to school on busy roads was to fear for their safety, and I responded in kind. I apologize to the students, their parents, and the community for a reaction that blew this incident out of proportion and called into question the character of our students. Our senior class has demonstrated leadership, unity and school pride throughout this school year. My actions and emotion overshadowed what should have been a very positive senior activity. I have learned much from this experience and do not consider myself infallible," she wrote, adding:  "I now applaud the students for their foresight in contacting the police department to ensure the safety of their senior surprise. I only wish the police department or others who may have known about this would have let us in on the surprise but, of course, it wouldn't have been a surprise had we known in advance."

The students' senior walk will take place next week, the day's absence won't be counted against them, and those who missed exams will be allowed to take a makeup without penalty, according to a report by WOOD-TV. They will walk on their graduation next week.

Parents had been incensed that their children were punished for celebrating school spirit, and they vented their frustration at a school board meeting Tuesday night.

"The disruption to the classroom, the disruption to the school day, was not these kids," Keri Whip, a parent of one of the bike-riding participants, told the board. "It was the principal."

Rachel Nicks, the mother of one of the participants, told ABCNews.com on Tuesday that the students should have been praised for their positive senior surprise, particularly because other schools' seniors have performed mean or malicious acts to mark their own departure.

"I think [Pennington] acted very hastily," Nicks said. "This entire town is, like, shook up over it. What's really kind of funny is that school spirit was turned into broken spirit."

The school district's superintendent, Gerald Hopkins, also issued a statement today that said the problem on Tuesday was that the "adults in school administration, the police department and city administration didn't communicate as well as they could."

"I take responsibility as the superintendent for ensuring better communication in the future. We will learn from this and be stronger for it. I apologize to the students, parents and community for not having arrived at a better solution," he wrote.