Ministry of Defence teaching materials that give an unbalanced view of the Iraq war are being used in schools, teachers' leaders have said.
National Union of Teachers general secretary Steve Sinnott claimed the materials produced for the MoD by a marketing agency could break the law.
He also claimed that youngsters from deprived backgrounds were being targeted by Army recruiters.
The ministry said teachers found the lesson materials 'valuable and fun'.
Mr Sinnott has written to the Schools Secretary Ed Balls about the lesson plan, produced by Kids Connections, which explores the topic of the ongoing occupation of Iraq by British Armed Forces.
He warned that some of its assertions, presented as facts, would be disputed by most teachers.
There were no estimates of the numbers of people killed, wounded or made homeless by the military action, he said.
The material therefore risked breaching the part of the 1996 Education Act concerned with balanced teaching of political issues, he added.
He told reporters: "When you are dealing with something as controversial as Iraq and the different events that led up to the invasion, teachers are under a duty to present material that is balanced.
"The MoD material does not live up to that high standard. That's what I have brought to the attention of Ed Balls."
Mr Balls responded to the union leader's letter saying his department did not promote or endorse any specific resources or methods of teaching for use in schools.
But he said he had asked officials to take up the matter with the MoD and appreciated Mr Sinnott's drawing it to his attention.
A spokesman for the Ministry of Defence said the programme concerned, which is known as Defence Dynamics, was a set of web-based resources whose use was completely voluntary.
"We have consulted widely with teachers and students during the development of these products and feedback from schools has been extremely encouraging.
"Teachers and students found them to be valuable and fun resources for applied learning.
"They are designed to support teachers in delivering a whole range of subjects across the national curriculum and its equivalents in Scotland and Wales."
He added: "We are happy to engage with the NUT to discuss further."
Mr Sinnott also criticised Army recruitment methods which he said did not present a balanced view of what joining the armed forces entailed.
He said "unethical practices" had been unearthed in recent research by the Joseph Rowntree Charitable Trust.
The teaching union will debate a motion at its upcoming conference on the ways in which schools are being asked to play a "partisan" role in war.
It argues: "Military intervention in schools customarily presents a partisan view of war, largely by ignoring its fatal realities in favour of promises of travel, skill training and further or higher education course sponsorships otherwise often unavailable to young people, especially in area of high unemployment."
Mr Sinnott said the recruiters engaged in "very dubious practices", targeting youngsters from poorer backgrounds.
"Youngsters from the most disadvantaged backgrounds have more limited opportunities in life than youngsters from better off backgrounds.
"It's simply a fact. I am not saying that youngsters from disadvantaged backgrounds cannot get something from a career in the military.
"The Army has created a better life for some youngsters, but there are other youngsters who join up because they have little or no choice."
But Mr Sinnott stressed that his words did not constitute an attack on the Army.