Constance Robertson, 25, is charged with felony carnal knowledge of a juvenile.
The incident was reportedly recorded on the student's cell and shared with other students.
The school immediately reported the allegation to police.
According the the School Board, Robertson has been working for the school system since May, 2017.
The teacher reportedly told officers that she thought the student was 18.
https://www.klfy.com/news/local/port-barre-high-school-substitute-teacher-arrested-for-having-sex-with-student/1525558836