Silenced (2011)

Gang In-ho, who is working to earn money for his daughter's surgery, is appointed to a school for hearing-impaired children in Gwangju. But what he discovers there is an ugly truth: the children are being physically and sexually abused by their teachers. When he decides to fight for the children's rights and expose the crimes being committed at the school, In-ho teams up with human rights activist Seo Yu-jin. But he and Yu-jin soon realize the school's principal and teachers, and even the police, prosecutors and churches in the community are actually trying to cover up the truth.