A textbook widely used in Victorian high schools describes the Crusaders who fought in the Holy Land in the Middle Ages as terrorists, akin to those responsible for the September 11 attacks.

The Year 8 textbook Humanities Alive 2 says that the Crusaders, like Muslim terrorists, "believed they were giving their lives for a religious cause".

"Like the Crusaders ... they were told they would go straight to heaven when they died," the book says. "Those who destroyed the World Trade Center (sic) are regarded as terrorists. Might it be fair to say that Crusaders who attacked the Muslim inhabitants of Jerusalem were also terrorists?"

The textbook has been criticised by Melbourne University historian Barry Collett, a specialist in medieval history, for being "historically inaccurate" and "grossly misleading" in its depiction of the Middle Ages.

"The Crusaders felt they were intervening to stop the bloodshed that was already going on," he said. "I would tend to compare them more with Australian troops intervening in East Timor."

The book, used in about 100 schools around Victoria, is a revised edition of a series of textbooks published by John Wiley and Sons since 2003, all of which have included the section on September 11.

The selection of textbooks is at the discretion of individual schools in Victoria and neither the Victorian Curriculum and Assessment Authority nor the state Education Department have any input into the quality or content of textbooks.

A spokesman for state Education Minister Lynne Kosky said schools decided for themselves what was appropriate to be taught and there were no recommended books for the curriculum.

The textbook also portrays the church as a corrupt institution driven by the desire for power and which tortured and killed anyone with opposing beliefs.

"It's very out of date, this view of the church as being fiendishly power-hungry," said Dr Collett, a visiting scholar at Oxford University.

"The church's activities were far more humane and pastoral than you would guess from reading this."

Dr Collett said the textbook presented an oversimplified view of history and the language used suggested a particular point of view rather than asking open-ended questions.

Despite popular perception, Dr Collett said those involved in the Inquisition actually spent most of their time working with divided families rather than torturing heretics.

Rather than working with government to oppress people, Dr Collett said the church was the principal force against the authoritarian excesses of governments.

General manager of the schools division at John Wiley, Peter van Noorden, denied the textbook makes a connection between the Crusades and September 11.

He said the section was intended to encourage discussion and prompt students to think more broadly about history. "It's very specifically put at the end of the section as a challenge for students to consider ... to analyse things from different perspectives," he said.

Dr Collett said the authors of the book included a historian, who worked closely with school teachers in developing the text and activities.