Twenty-year-old Phillip Jerrod Barham worked at Southeast Raleigh High School until he resigned Wednesday.
Investigators said his alleged victim was not a student at the school.
Barham is charged with one count of statutory sex offense.
In court Wednesday, Wake District Judge Jaquie Brewer told Barham he faces a possible felony conviction.
"If you plead guilty, or you are convicted of that offense, the maximum possible punishment is life without parole," said Brewer.
Barham's mother told the judge they'd be hiring a lawyer.
Another woman - apparently Barham's sister - said the charges are not true.
"She made it all up. She made it up. (name deleted) made the whole story up," she said.
Barham's bond was set at $800,000.