According to officials, 40-year-old Ronette Ricketts, of Poughkeepsie, used a screwdriver to stab fellow English teacher Cynthia Glozier, 52, of Rhinebeck, during an altercation in the second floor hallway.
It's not known what led to the fight, but students said there had been some "bad blood" between them.
Both women are well known and longtime educators at the high school. Before becoming a teacher, Glozier worked as a supervising producer at Court TV. She was rushed to St. Mary's Hospital, where she was listed in stable condition.
Ricketts was taken into police custody and charged with assault in the 2nd degree and related charges.
She was ordered held at $50,000 cash or $100,000 bond. She was unable to post bail and she was remanded to the Dutchess County Jail.
The school was locked down for about 75 minutes after the incident.
Classes at Poughkeepsie High School continued, but some periods were shortened or eliminated.
No students were involved in the incident and no students were harmed. No other staff members were involved in the incident.
The high school said counseling was made available to students and staff who desire assistance.