The teacher suffered non-life-threatening injuries.
Cy-Fair ISD confirmed an altercation happened inside the school restroom, putting the campus in "secure the building" mode Wednesday morning.
Authorities say the student was stabbed on campus during a fight with another student, and despite emergency medical care within just seven minutes, she couldn't be saved.
School officials said the incident started as a physical altercation between two students from Wharton County Junior College who began assaulting a former student.
Police arrested Pablo Castaneda last week after HISD said he stabbed a Sterling High School classmate. Prosecutors now say the 17-year-old may face more charges for what he allegedly did after court.
The stabbing, which occurred during a fight on campus, is just the latest attack in a string of school violence, with some parents saying they are "tired of this."