The Supreme Court ordered a retrial Thursday for three men convicted of raping a school teacher amid criticism that the previous ruling was too lenient.

They were indicted in June last year for colluding and collaborating to sexually assault a female teacher at their children's school in an island town in Sinan, about 400 kilometers southwest of Seoul.

Investigation showed they failed to rape her initially because of her resistance. They raped her after forcedly intoxicating the victim. They also filmed the scene.

The prosecution demanded 17 to 25 years, but a lower court handed down 12 to 18 years, clearing them of colluding and collaborating on the first assault. An appeals court further reduced their sentences to between 7 and 10 years.

The top court found that their initial attemped rape was also planned and committed together, indicating that the defendants deserve heavier punishment. The court sent the case back to the Gwangju High Court.