The Institute of Public Affairs (IPA) has been accused of tprying to indoctrinate school children by distributing a classroom lesson plan that teaches students how to mount arguments against the proposed Indigenous Voice to Parliament.

The conservative think tank has paid for multiple Facebook and Instagram ads promoting high school education materials it says gives teachers "the tools you need to walk your class through both sides of the referendum".

The ads link to a free, 34-page teacher guide and workbook the IPA has written for year 9 to 12 students in English, Australian History, Civics and Indigenous studies.

While the lesson plan promises to teach students about all sides of the debate, the main written exercise asks them to present the "No" case.

It asks students to refute a series of statements supporting the Voice using an almost 1,000-word summary of various "No" arguments.

Students are then asked to rank the arguments in order of persuasiveness and then "respectfully discuss with your peers".

They are not asked to repeat the exercise from the "Yes" perspective.

Students are also asked to complete a true/false quiz that includes the statements, "Anyone who votes No in the Voice Referendum must be racist" and "There are no acceptable arguments for voting No in the Voice Referendum".

The Australian Education Union (AEU), which reviewed the materials, described the lesson plan as a "shallow attempt to inflict their conservative views on students in schools".

"We will fiercely oppose any such moves by private and political organisations that seek to indoctrinate students," AEU federal president Correna Haythorpe said.

"This move by the IPA can only be viewed as a cynical attempt to influence and interfere in Australia's democratic processes via the education system."

The AEU has pledged its support for the Voice but has not told its members how to vote in the referendum.

The IPA's deputy executive director Daniel Wild rejected the criticism, saying: "you would expect the AEU to say that".

"It is on the record as explicitly supporting the Voice to Parliament, which completely undermines the AEU's capacity to provide students and teachers with a balanced view on this critical matter," he said in a statement.

"The AEU is not the sole arbiter of truth, and it is deeply concerning that they are seeking to prevent open and balanced analysis occurring in classrooms ahead of this vital referendum."

The Melbourne-based IPA told ABC Investigations that it "does not support or oppose the Voice to Parliament", despite listing itself in the lesson plan as a resource for students looking for more information about the "No" position.

"Teachers in the classroom are in the best position to determine what materials to use in class, not union lobby groups which are explicitly campaigning for a Yes vote," Mr Wild said.

The teaching resource was developed as part of the IPA's "Class Action" campaign, which has produced a range of lesson plans and other teaching materials it says complement compulsory high school humanities subjects.

On its website, Class Action argues Australia's National Curriculum "carries undertones of Critical Race Theory … a reframing of Western Civilisation through the lens of guilt, and a reduced academic rigour .. where social sensitivity is given primacy over critical thinking".

"The IPA's Class Action research program was established to consider the values of Western Civilisation, and to contribute to a flourishing future of Australian society that knows its roots and can humbly acknowledge its imperfections without erasing its proud achievements," Mr Wild said.

The IPA approached multiple state-based history teacher associations in the past six months and asked for them to share the Class Action lesson plans with members.

Some state associations told ABC Investigations they agreed to alert members to the resource kits, but did not actively encourage or promote their use. They said they were unaware of any teachers using the lesson plans.

"Since Class Action material packages research specifically for use in classrooms it is natural we have let teachers know through multiple channels, including their professional associations," Mr Wild said.

In response to ABC Investigations' questions about whether any teachers had used its Voice to Parliament lesson plan, the IPA said: "according to our analytics, approximately 3,000 Australians have accessed the resources supplied by Class Action in the past month."

Education and history experts who independently examined the document raised concerns about its accuracy, effectiveness as a teaching tool, framing of Indigenous issues, and its lack of balance.

Monash University History Professor Bain Attwood, who supports the Voice, described the document as an "act of bad faith" from the IPA.

He said the resource was "egregious" for presenting itself as impartial.

"What it's clearly trying to do is essentially persuade those who read [it] that the arguments against the proposal are more persuasive and more convincing," he said.

"There's not sufficient material in the resource to help students make sense of and critically evaluate the arguments."

Claire Golledge, a lecturer in secondary education at the University of Sydney who supports the Voice to Parliament, said the exercise format asking students to address individual arguments was a common teaching tool but echoed Professor Attwood's concerns about the lack of balance.

She added there was misinformation in the Vote-No points which were presented without context.

"When you dive into some of the content of those arguments… a lot of those arguments have been credibly challenged by pretty learned experts," Dr Golledge said.

Mr Wild dismissed suggestions the material contains misleading information.

"As the lesson plan makes clear, these are possible No arguments which could be made, and that students are encouraged to critically evaluate," he said.

"One may agree or disagree as they see fit, in conjunction with other materials, as the Class Action lesson plan makes clear."

The IPA says the lesson plan also points to further resources regarding the Yes case, specifically The Uluru Dialogue and Uphold and Recognise.

Professor Attwood, who has published extensively on the history of civil rights in Australia, also took issue with how Indigenous history was framed in the resource.

"It doesn't explain effectively why this referendum is so important from the point of view, at least, of Aboriginal people," he said.

"It doesn't really describe how oppressive and discriminatory this history [through] large swathes of the last 200 years has been."

He said the classroom materials made reference to discriminatory legislation but overall was not an "adequate account of the history of Aboriginal people in this country".

Professor Attwood said if he discovered this lesson plan was being used in his child's classroom he would "immediately contact the principal and make representations that this resource be removed from the school".

Mr Wild denied the materials were designed to persuade.

"Mr Attwood appears to be under the misapprehension that these materials are designed to persuade, when they simply inform teachers of the various arguments regarding the Voice to Parliament," he said.

"The lesson plans are designed to be consistent with the requirements of the National Curriculum, and teachers are free to use these materials should they find them of value."