The Scottish Government has been urged to allow parents to withdraw their children from all lessons promoting same-sex relationships.
The Free Church of Scotland claims pupils should not be forced to listen to controversial teaching that is in direct opposition to strongly held religious beliefs.
The denomination said provision to allow people of no faith the option to withdraw their children should they so desire was in place.
The Rev James Maciver, principal clerk of the Free Church’s General Assembly, said: “Given that two-thirds of respondents to the Scottish Government’s first consultation opposed the redefinition of marriage, to date the largest public opinion poll on the subject, it is clear it remains a deeply contentious issue amongst wider society.
“We urge the government to extend the right to withdraw pupils to cover all lessons designed to promote same-sex marriage as a morally acceptable marriage form.
“Otherwise parents opposed to the teaching of same-sex relationships will have no control over what their children are being taught, where such teaching would be in direct opposition to their religious beliefs.”
Professor James Fraser of Kiltarlity, near Inverness, chairman of the Free Church’s board of trustees, said the denomination was concerned that the state had begun to take the view that beliefs in same-sex marriage should be promulgated to every child whether or not parents share the beliefs.
A Scottish Government spokeswoman said: “Relationships, sexual health and parenthood education is an integral part of the health and wellbeing area of the curriculum.
“It is for local authorities and schools to decide how it is delivered, based on local needs and circumstances.
“We expect schools to take seriously all requests to opt children out of aspects of sexual health education.
“All such requests should be discussed with parents or carers and, where the child is old enough, the child.”
The spokeswoman said guidance for teachers on the subject was currently being considered and is expected to be shared with schools by the end of the year.