The student, a female, apparently made the threat on Snapchat. The FBI caught wind of the threat and began investigating the student.
The agency tracked the girl to Stamford High School and transferred the information over to the local police.
Police and a school resource officer located the student and placed her under arrest.
No weapon was recovered on the girl at the school.
Police investigated and searched the residences of the girl's parents but did not recover any weapons.
She was taken to Stamford Police headquarters and charged with threatening in the first degree and breach of peace.
The investigation is ongoing as authorities work to collect more information from Snapchat.
The arrest comes as questions are being raised about parental liability in school shootings.
The student is due in court on September 13.