A 29-year-old woman has been arrested in New Jersey for allegedly posing as a high school student. Ms Shin attended the school for four days before staff found out her age.
The woman, identified by police as Hyejeong Shin, has been charged with using a fake identification document to enrol in New Brunswick High School.
School officials said police are investigating the matter, and a review of the district's enrolment process will be conducted.
The issue came to light at a local education board meeting on Tuesday, where New Brunswick Public School District Superintendent Aubrey Johnson told attendees that Ms Shin was caught at the school.
"Last week, by filing some false documents, an adult female posing as a student was able to be enrolled in our high school," Mr Johnson said.
He added that she had been in a few classes and spent some time with guidance counsellors, who tried to find out more information about her.
Ms Shin's false age was then uncovered, Mr Johnson said, and the school immediately notified police.