"A "hit and run" approach to teaching children how to protect themselves against molesters was not enough, Ms Nancy McBride said.
Ms McBride, executive director of the National Center for Missing and Exploited Children in the USA, said the best way for children to learn was through repetition, not just one visit to the classroom by a local police officer. A programme should be put in place from kindergarten.
She said murders and crimes against children were rising. In the US, there had been a 6 per cent rise in child murders over the past 15 years. In England and Wales, there was an average of 85 unlawful killings of children a year.
Most of the crimes against children, particularly sex abuse, were carried out by people known to the child. Most molesters were men and, characteristically, they got on better with children than with adults. They managed to get themselves into positions where they had children in their care.
"We need to dispel the myth of the stranger in the dark. You know that when you go into a courtroom where a molester is being prosecuted it is impossible to pick him out from the attorneys or anyone else. He looks just like everyone else," said Ms McBride.
She said children needed to be taught "not to get too close" to people they did not know, particularly men in cars. "Teach them not to give directions to people. If an adult is going somewhere they shouldn't need to ask a young child."
However, telling children to stay away from all strangers was not always correct.
"If a child is lost in a mall what can they do? You have to teach them about low risk strangers, such as store clerks, policemen or a pregnant woman with children."
She said people who molest must serve all their sentence. A sex offenders' register should be introduced, along with a community notification system where people were aware if a convicted abuser moved into their neighbourhood.