The attack occurred just after 2 p.m. inside the library of Fannie Lou Hammer Freedom High School in the Bronx, the New York Police Department told Fox News.
A 16-year-old stabbed an 18-year-old in the back, stomach and leg, police said. The victim was taken to a hospital in stable condition.
A NYPD police spokesman was not aware if the stabbing suspect was taken into custody or what led to the attack.
Fox News has reached out to the school but has not heard back.
As of Sunday, the city experienced 9,647 reported robberies, compared to 9,686 in the same time frame in 2020. Felony assault, however, increased with 16,889 reports. That figure represents a 7% jump from the 15,787 reported last year.