By Guy De Launey
BBC News, Phnom Penh
A former Khmer Rouge prison guard helped distribute the new textbook
Students can rarely have seemed so enthusiastic about receiving a textbook.
Even though it was not a school day, dozens of them made their way in to Sisowath High School in the centre of Phnom Penh for a presentation ceremony.
School and government officials were formally handing out the new Khmer Rouge history book, a scene that will be repeated across the country in the closing months of this year.
Three decades have passed since the fall of the Khmer Rouge government. Yet only now are Cambodian schoolchildren finally starting to learn about what happened during the Pol Pot era.
As many as two million people died in the late 1970s from forced labour, malnutrition and the summary execution of so-called "enemies of the revolution".
But the subject was conspicuous by its absence from the high school curriculum until the new textbook received official approval.
At Sisowath High, the students enthusiastically fired questions at the book's author and an official from the ministry of education. They asked "Who were the Khmer Rouge?" and "Why did they kill their own people?"
These are the kind of things which one might have thought they would already know. But official information has been thin on the ground. Until now the official school text contained a mere five lines on the Pol Pot era.
Khamboly Dy has expanded that paragraph to an entire textbook for the Documentation Centre of Cambodia, an organisation which gathers evidence about Khmer Rouge atrocities.
WHO WERE THE KHMER ROUGE?
Maoist regime that ruled Cambodia from 1975-1979
Founded and led by Pol Pot, who died in 1998
Abolished religion, schools and currency in a bid to create agrarian utopia
Up to two million people thought to have died from starvation, overwork or execution
Like most Cambodians, he was born after the fall of the Khmer Rouge - but he insists young people must not ignore the subject.
"After the Khmer Rouge regime, Cambodia was so damaged and fragile - like broken glass," he says.
"The young generation has the responsibility to repair this broken glass. They need to understand what happened in their country before they can move forward to build up democracy, peace and reconciliation."
Teaching the Khmer Rouge era has not been straightforward in Cambodia.
The subject disappeared from the curriculum in the early 1990s when Pol Pot and his followers were among the signatories to a peace agreement.
A series of defections and the presence of former Khmer Rouge members in the current government mean it is still a sensitive issue to tackle.
So the new textbook is careful to concentrate on the grim facts of the Pol Pot era, rather than any political analysis. And that has ensured its official approval.
There are chapters titled "forced labour", "purges and massacres" and "interrogation and torture" - but no explicit photos.
Seventeen-year-old Rina was among the first students at Sisowath High to receive the textbook - and looked forward to closing the gaps in her knowledge.
Like Rina, most Cambodians were born after the Khmer Rouge fell
"I feel regret and guilty about this; they killed a lot of people," she explained.
"The new textbook will give me the experience of what happened in Cambodia - and Cambodians will never let this happen again."
The absence of the Khmer Rouge era from the school curriculum meant young Cambodians had been relying on older family members for information.
Researchers discovered that some found the horrific stories barely believable, and cast doubt on whether the atrocities actually happened.
Those attitudes may now change. Sisowath High School history teacher Im Sao Sokha will be among those using the new textbook to guide students through Cambodia's bloody past.
Teacher Im Sao Sokha lived through the Khmer Rouge era
"I lived through this period myself," he says.
"No other country killed its own people like this - it was a disastrous episode in Cambodian history. If they understand what happened during the Khmer Rouge, students will change their attitude. They won't get involved with conflict, violence or fighting with each other."
It is a lot of weight to put on a single textbook. But at the very least it should help to ensure that young Cambodians have the full details of the events of the Pol Pot era. What happens next is up to them.