Former students from private schools in Sydney are grappling with a troubling question: What happens when freedom of religious expression strays into misinformation?We have spoken to more than 30 former students from elite schools associated with the small but powerful branch of the Catholic Church known as Opus Dei.The students have made disturbing claims about the messaging at the schools, which they say at times deviated from the curriculum and veered into misinformation.Students say they were told that masturbation was mentally disordered behaviour, homosexuality would send them to hell, and girls were discouraged from getting the HPV cancer vaccine because it encouraged promiscuity.For some, their schooling has left them with deep psychological scars.The schools and the Opus Dei community have strong ties to the NSW Liberal Party. Premier Dominic Perrottet is an Old Boy.Faced with questions from Four Corners about the schools' practices, Mr Perrottet has referred the allegations to an investigation by the NSW Educations Standards Authority.But tonight on Four Corners former students warn that parents and others in the community are in the dark as to what is going on behind the school gates.