Sgt. Christian Dinco says the 16-year-old was repeatedly asked for money by the man at 7:30 a.m. Tuesday while she was walking to Martin Luther King High School.
To get away from the suspect she walked to the back of some businesses, but the man followed and attacked her.
Dinco says the suspect punched her in the face four times before pulling a knife and cutting her arm.
The suspect fled on foot and remains at large.