Teens at Westchester Square Academy in the Bronx said they’re on edge after a 28-year-old woman allegedly attended class pretending to be a student for weeks.

“I was literally, like, terrified,” said Jamie Demmitt, 14, a first-year student at the public school. “I don’t feel safe anymore.”

Kacy Claassen’s brief stint under the pseudonym Shamara Rashad was the talk of the school on this week. Some students described Claassen as “an old lady,” while others said she had a youthful appearance. One student said Claassen had tattoos of a moon and a demon on her chest. Others recalled her as an active participant in class, asking questions and seeking extra help from teachers.

“I saw her in the back of the class, doing her work,” said sophomore Sebastian Hernandez, 16. “She just acted like a student. She was asking the teachers questions. Like everybody.”

Prosecutors say Claassen enrolled at Westchester Square Academy in April, telling school officials she was just 16 and had recently moved from Ohio to New York with her sister.

Westchester Square Academy has about 400 students and is co-located with several other schools on the large Herbert H. Lehman Campus in East Tremont.

Students wondered how she was let into school in the first place.

Hernandez said the bizarre episode had left him rattled. “It made me feel like our school’s not safe and more things can happen,” he said.

Demmitt said she saw Claassen attend teachers’ office hours.

“She would stay every day after school and every day before school. And she would take time from other kids … which wasn't right, because I actually needed help … and she would take my time,” she said.

Deborah Alexander, a representative from the Bronx on the Citywide Council on High Schools, a parent advisory board, said the incident is disturbing and makes her question whether the city’s enrollment process needs improvement.

“Parents should never have to question whether basic safeguards are being followed, particularly when it comes to who is in the building,” she said.

Education department spokesperson Isla Gething said the department is “providing all necessary and suitable support” to the school community. School leaders notified parents of the incident.

“Enrollment fraud is a serious crime that fundamentally undermines New York City Public School values,” she said.

Gething did not immediately respond to questions about how Claassen enrolled, including how she managed to pull it off without a parent or guardian.

Demmitt, who had math, biology and gym classes with Claassen, said the vibes were off right from the start.

“We all were saying she looks, like, really old,” she said, adding that Claassen had a lot of tattoos on her chest, including of a moon and a demon. “You could tell she was not our age.”

She said Claassen was “acting really weird” and would “ask stupid questions.”

Demmitt recalled one strange disruption during a class.

“She just started sneezing and ran out of the classroom,” she said. “We were all saying how it was weird.”

According to the complaint, Claassen attended Westchester Square Academy for two weeks until the principal confronted her with a screenshot of her Facebook page, which included her real name and date of birth.

Claassen then admitted to the principal she lied, saying her friend “forced” her to enroll in school “to receive more public assistance,” according to the complaint.

She was charged with criminal impersonation and trespass and pleaded not guilty.

Her attorney declined comment.

The school was put on “a hold,” with students required to remain in their classrooms, during the arrest.

Hernandez, the sophomore, said he was shocked to find out the new student sitting in the back of the class was actually an adult. “The next day, everyone is talking about [how] she’s a woman, a full-grown woman,” he said. “And I’m just so surprised because I thought she was 15. She acted just like a 15-year-old, doing her work and everything.”

Students said the school sent letters home with kids informing their parents of the situation.