The student, who has not been named, had just returned to school after serving a three-day suspension, according to school officials.
Staff members immediately called 911 and the student was arrested. Principal Dr. Jill Hudson was not seriously injured in the attack.
Parents learned of the scary incident via a Thursday robo-call from school administrators.
"I got the call. I was at home waiting for him to come home, and I heard it on the answering machine," said parent Jane Witmer.
The call went on to say that "staff acted quickly and the student will not be allowed back."
Stephanie Ackaret's nephew attends the school, and she said news of the attack came out of left field.
"In the three years he's been attending the school we've never had any incidents, at least that I've been aware of," she said.
Like many other parents, Witmer said she was reassured by how the school handled the situation.
"I didn't know how they handled it specifically, but I know the school has a culture of cooperation and community and I feel confident they handled it as best they could," she said.
School officials say they "take the safety of all our students and staff very seriously" and ask parents to contact the main office if they have any questions about the incident.