The parent of an elementary school student recently filed a child abuse claim against her child's former teacher, a Seoul teachers' union said Thursday, after sending a threatening letter to the teacher regarding the teacher's daughter.

The parent in question filed the complaint over alleged child abuse Wednesday, two days after being questioned by police for the threat letter sent last year, according to the Seoul branch of the Korean Federation of Teachers Unions. She claimed that her child -- now attending another school -- had been subject to emotional abuse.

The disagreement between the parent and teacher began in May of last year when the parent's child was not included in a group photo of some classmates. The teacher explained that the group photo was taken at the request of some students and did not include every student, but the parent repeatedly issued complaints.

Last July, the parent said in a letter sent to the teacher that she "better keep reading if you don’t want anything bad to happen to your daughter," adding that she learned that acquiring personal information and "doing something" is very easy if one has the money. It was also reported that the mother secretly recorded the teacher without her knowledge, which she used to blackmail her.

The parent claimed that her complaint was not solely because of the photo, saying she had been a teacher herself. She did not elaborate on other factors that led to her sending the letter but emphasized that her child was a model student.

The Seoul Metropolitan Office of Education stepped in and filed criminal charges against the parent for familial intimidation and unlawful obtainment of telecommunications content. The teacher also filed for charges including coercion, false accusation and obstruction of the performance of official duties.

The news comes as teachers across the nation commemorate the first anniversary of the suicide death of a 24-year-old teacher at Seoi Elementary School in 2023. Her death was suspected to have been induced by stress from excessive interference from students' parents. However, police found no evidence indicating foul play and closed the case without pressing criminal charges after four months.

Teachers and rights groups have been calling for reinvestigation of the case.

The KFTA and other teachers' unions have set periods of remembrance and are holding memorial services nationwide.

"Nothing has changed from the Seoi Elementary School teacher's death a year ago. Enduring the actions of a parent with malicious intent is solely up to the teacher," the Seoul teacher in the recent case told local media.