Prejudiced parents are abusing their right to withdraw children from RE lessons, according to teachers.
Mothers and fathers who selectively remove youngsters from classes due to their own biases can hamper schools' attempts to "prepare a child for life in modern Britain", the National Education Union (ATL section) annual conference has heard.
Delegates have agreed a resolution urging the Government to take steps to prevent parents from selectively withdrawing their children, specifically from the teaching of individual religions.
Proposing the motion, Richard Griffiths from the union's Inner London branch, said that RE today has developed into a subject "that allows for critical thinking, big questions, allows children to explore their own and other religious beliefs and non-beliefs".
He said the resolution was not against parents' right to withdraw youngsters, but was concerned about evidence which suggested an increase in the abuse of the right, and the potential for it to be abused.
Mr Griffiths argued that the right in the "rare cases" where parents' religious beliefs provided genuine grounds for withdrawal was "very different to the cases of parents with certain prejudices including Islamophobia and antisemitism who wish to remove their children from certain lessons or visits to places of worship that would significantly hinder the ability of the school to prepare a child for life in modern Britain".
He highlighted a recent Press Association investigation which indicated that there had been a 48% rise in hate-related crimes linked to race and ethnicity between 2015/16 and 2016/17.
Mr Griffiths told the conference: "I'm sure you are well aware of the dangers of members of society closing themselves off to the rest of the world, the dangers of social media channelling an ever more extreme reflection of people's beliefs, without balance, and the dangers of those children who are ignorant of other religious beliefs and non-beliefs, and lack an understanding of the way that individuals, regardless of religion, can work together and make a positive difference to society are increasingly vulnerable to targeting by extremists."
Kim Knappett, the union's vice president, said she had been shown a letter by a headteacher from a parent who was asking to selectively remove their child from RE and that "the letter was so foul" her answer was that they should refer it to the relevant authorities.
She said in another case, she had been talking to students of different ages about RE in sixth forms and they told her they believed it was important that they learn about each other, and to question and debate.
The motion urged the union to work with others to "determine the nature and extent of the selective use of the right of withdrawal".