CLAREMONT — Two threats of school violence resulted in the cancellation of classes Friday at one Upper Valley high school and a heightened police presence on several campuses.

SAU 6 Superintendent Chris Pratt said in a Thursday evening message to the families he was canceling classes at Stevens High School because of a message threatening an act of violence on Friday.

Stevens was the only school in SAU 6 — which includes Claremont and Unity — identified in the message and therefore Pratt said classes at the middle school and three district elementary schools went ahead as scheduled. Parents, however, could choose to keep their children home if they so desired.

“As both your Superintendent and as a parent myself,” Pratt wrote in his Thursday message, “I want to be as transparent as possible so you can make the decision you feel most comfortable about sending your student to any of the other schools.”

Pratt wrote that he could not justify holding classes in the face of “uncertainty” and there would be police patrols at all district schools.

Police also were present Friday morning at both the Royalton and Bethel campuses of the White River Unified District.

Their presence came in response to “alarming social media posts” about a student “allegedly bringing a gun to school,” Superintendent Jamie Kinnarney told families in a message Friday.

“We will have police on campus throughout most of the day today and they will definitely be on campus during dismissal,” he wrote.

The threat was subsequently investigated by local police and the Windsor County Sheriff’s Department who “determined that there was never a credible threat to school safety,” Kinnarney said in a followup message.

Windsor County Sheriff Department investigated and conducted interviews with the students involved, leading them to conclude there was never a threat to students or staff, Sheriff Ryan Palmer said in a news release Friday afternoon.

The department “learned that the messages were posted based on (thirdhand) information and there was no credible link to” the student, Palmer said.

In Claremont on Friday, police were working with the school district to identify the person who sent the email Thursday “indicating there would be some sort of an active attack today,” Claremont Police Chief Brent Wilmot said.

He said the email was sent to seven or eight students and one staff member but he could not say who alerted school administrators.

Once the sender is identified, authorities will make a “risk assessment” of the situation and decide if it warranted administrative action by the school district or criminal justice action on the part of police, Wilmot said.

A message left for Pratt, the SAU 6 superintendent, on Friday was not returned.

“Threats like this happen too often in school and we cannot take risks in this day and age,” he wrote in his message to families.

Patrick O’Grady can be reached at pogclmt @gmail.com.