The incident occurred during a morning confrontation at Spring High School, 20 miles north of Houston. Three people were in custody and being questioned by investigators, the Harris County Sheriff's Office said.
The 17-year-old victim died at the scene of the attack. Two of the injured were treated at Houston Northwest Medical Center and the third victim was taken to Memorial Hermann Hospital in the Texas Medical Center. Two of the victims suffered minor injuries.
One of the injured victims was Deaveon Brazil, 16, a junior at the school, KHOU-TV, Houston, reported. Memorial Hermann Hospital upgraded his condition from critical to serious several hours after he arrived, a hospital spokesman said. The other victims are unidentified.
The school remained on lockdown for the rest of the day, CNN reported.
Investigators are looking into suggestions that the stabbings were related to gang activity. "However, deputies had not been called to the school about gang violence before today," the sheriff's office said in a statement.
The Rev. E.A. Deckard of Green House International Church -- acting as spokesman for the family of one of the victims -- said the incident was not gang violence but "simply a misunderstanding between two people" in a dispute that had been going on for some time, the Houston Chronicle reported.