Heads warned Gillian Shephard, the Secretary of State for Education, against a "panic reaction" as she said proposals to be issued on Friday on teaching morals in schools should put more emphasis on the family.
A row over the document surfaced earlier this year when traditionalists argued that the plans, drawn up by the Government's curriculum advisers, did not do enough to promote marriage and the family.
Mrs Shephard, who is considering a draft report on morals in schools by the National Forum for Values in Education and the Community set up by the School Curriculum and Assessment Authority, stopped short of saying it should advocate traditional marriage.
She told GMTV's Sunday programme that strong families were of inestimable value to society. "We must look at ways that we can strengthen that side of the report ... before it actually goes in anything that we might instil in schools."
Nick Tate, the SCAA's chief executive, said yesterday that the forum had not set out to draw up a "new 10 commandments". Schools were already moral places and it was up to the Government to decide whether there should be a programme in schools backing marriage.
He added: "Many people on the forum wanted the statement to be much more specific about the position of the traditional family. But that wasn't the task. It was to find a consensus on the minimum on which all could agree. Some people feel you can have a good family without it being based on traditional marriage."
But David Hart, general secretary of the National Association of Head Teachers, accused politicians of "falling over themselves to gain the moral high ground. Mrs Shephard should think again before interfering with the recommendations on moral education in schools. Morals are not the preserve of those who are married".
The document suggests that schools should teach pupils to value truth, human rights, the law, justice and "collective endeavour for the common good of society".
Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers, said: "It is absolute nonsense from beginning to end. Morality is caught, not taught. If leaders in every walk of life showed they believed in family values, then children might be different."
Ministers say the Education Bill to be published this week will give schools new powers in the fight against indiscipline. It comes as inspectors go into the Ridings School in Halifax, where teachers are demanding the exclusion of 60 pupils.Reuse content