This picture shows the exterior of the National Police Agency building in Seodaemun District, Seoul, June 27, 2022. Korea Times photo by Hong In-ki

Police have referred an incumbent high school teacher to the prosecution for making college entrance exam questions and selling them to a private cram school for some 250 million won ($ 180,072) over the course of four years, officials said Monday.

The National Office of Investigation (NOI) under the National Police Agency said it has booked 69 people and referred 24 of them initially to the prosecution as part of investigations into the collusive "cartel" ties between public and private education sectors.

A total of 24 such cases are under investigation, officials said.

All of those referred to the prosecution were incumbent high school teachers working in Seoul.

They allegedly received between 100,000 won and 300,000 won per question.

Notably, a high school teacher was charged with violating the anti-graft act for selling questions to a large private academy in return for 250 million won from 2019 to 2023.

The teacher is also accused of taking part in a review panel for one of the state-administered mock tests last year, using the information gained from there to make 11 questions and selling them to two private institutions.

The teacher denied any wrongdoing, saying there was no correlation between the mock test and the questions he sold to the private institutions, but the police confirmed the similarities based on expert evaluations, officials said. (Yonhap)