Church leaders and family groups have reacted angrily over plans to let 14-year-olds give sex education lessons to younger kids.
They will dish out advice on issues like puberty and contraception, as well as telling kids as young as 11 where to get information on gay issues.
The scheme is being piloted in Dundee in a bit to combot the city's teenage pregnancy rate - the highest in Europe.
The £45,000-a-year initiative was launched at the end of last year and could be introduced at other schools across the country, depending on its impact in Dundee.
However, the Catholic Church branded the move "flawed". A spokesman said: "The legal age for sexual intercourse is 16. This initiative is the equivalent to having 15-year-olds teach younger children how to drive a car.
"All the evidence suggests the decades we have wasted on such flawed approaches have been counter-productive."
And Norman Wells, director of the Family Education Trust, criticised the initiative for placing too much responsibility on pupils.
"Parents and teachers should not be abdicating their responsibilities in this way and using schoolchildren to offer advice in areas where they lack the necessary wisdom, experience and maturity.
"The last thing children and young people need in school is to be bombarded with yet more sexual images and language.
"What they really need is to develop the character qualities that will enable them to establish a strong, stable, trusting marriage in years to come."
But the move has been welcomed by the Scottish Parent Teacher Council. Spokeswoman Eleanor Conor said: "Youngsters will probably relate better to children nearer their own age than adults."
Elizabeth Fordyce, convener of Dundee City Council's education committee, said: "I think when you have young people talking to and teaching other young people about issues likes this, there’s more of a chance of them listening.
"We have a lot of older teachers and although they may be very good, when it comes to sex education a lot of the younger pupils will just not engage with them because of the age difference.
"Dundee has a really bad reputation for teenage pregnancies and this has been brought in to try and tackle that."
