The incident took place on Wednesday, June 9, and involved a male student at Bunnell High School in Stratford, suffered a self-inflicted wound.
"The student used a knife to cause the injury to himself," Stratford PD Captain Frank Eannotti said.
As a result, the school was temporarily placed in lockdown until police officers and medical personnel arrived and the student was transported to a local hospital for treatment.
The student is currently listed in stable condition, police said.
The incident is still under investigation. No names will be released due to the age of the student involved.
The Stratford Board of Education will determine the schedule for the remainder of the school week.
"This was an isolated incident of self-harm and no other students were harmed," Eannotti said.
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