Caitlyn Abercrombie, 15, is recovering from surgery.
Students were forced to leave the school, which is near Fayetteville, on Monday with their hands over their heads.
Later, police took two students into custody, a 15-year-old and an 18-year-old.
WATCH: Police question two suspects in campus shooting of teen
Students at lunch said they saw the victim fall to the ground but nobody saw a gun.
"She was bleeding from the neck, and that's when everybody started running," said a classmate.
"Did anyone see a gunman?" the reporter asked.
"No, we just heard a shot," said another student.
Some parents told WTVD on the scene they thought the shooting stemmed from a gang-related incident last week.
Police said they do not believe the girl was targeted.
Classmates set up a Facebook page urging people to pray for Abercrombie.
FACEBOOK: Prayers Go Out To Caitlyn Abercrombie
The 18-year-old suspect is scheduled to appear in court Tuesday in connection with the shooting.
The 15-year-old suspect will go to juvenile court, although an exact date for the student's appearance wasn't known, sheriff's office spokeswoman Debbie Tanna said.
Sheriff Butler said the two teens were caught with the help of surveillance video which showed them carrying the rifle inside the school. The suspects were either in the hallway with the door open or outside the breezeway where Abercrombie was walking.
While the high school has metal detectors, Butler said he didn't know if they were used on a daily basis at the school.