We had been summoned to the headmaster's study.
After WWII, the US remodelled Japan's school system on their own
Toru Sato runs one of the top high schools in Tokyo. His 900 pupils are some of the city's best academic performers, yet he was sweating and nervous.
Would we agree not to show any of the faces of the students we had filmed, he asked.
Could we assure him we had not recorded any of the national anthem? He looked desperate.
"Why?" I asked. He had given us permission to film what seemed to be a perfectly ordinary ceremony, welcoming the new students on their first day.
We had watched them walking in under the cherry blossom, accompanied by proud parents, and sitting down in the school assembly hall.
The only difference from previous years was the distinctive rising sun Japanese flag, placed centre stage next to that of the city government. Nothing obviously controversial about that.
But as they were about to strike up the national anthem, we were told to leave.
Nearly 60 years after it surrendered to the United States and renounced the militarism of the 1930s and 40s, Japan still cannot decide what kind of country it wants to be.
Hundreds of teachers registered their objection by refusing to stand up
This manifests itself in all sorts of ways, from the agonised debate over sending a few hundred troops to Iraq and the furious attacks on the prime minister's visits to the national war shrine, to the row today over playing the national anthem in school.
Many of the symbols of the disastrous era of military rule still survive in Japan - the emperor, the flag, the national anthem - but their exact status has been left deliberately vague.
It was only in 1999 that the ancient poem Kimigayo, calling for the reign of the emperor to last "for all eternity" was formally declared the official national anthem once again, as it had been before the war. But many Japanese still object to it.
So when the Tokyo city government this year decided to enforce playing Kimigayo at the beginning and end of the school year, hundreds of teachers registered their objection by refusing to stand up.
They did not reckon with the determination of Shintaro Ishihara, the unapologetically nationalist governor of Tokyo.
Toru Kondo has had an unblemished career as an English teacher for 31 years.
Now, spluttering with rage, he opens an envelope to show me his first ever official warning from the Board of Education. He is one of those who refused to stand.
Governor Shintaro Ishihara is a controversial public figure
"Japan changed after the war," he says. "Our constitution gives us freedom to follow our consciences. This cannot be a democratic country if they insist on punishing us."
Like many teachers in Japan, Toru Kondo's politics are left-wing, and like most left-wingers here, he has an unforgiving view of anything connected to his country's shameful past.
Never mind that the lyrics of Kimigayo are innocuous, and today's emperor has only symbolic, not divine status.
The city government, though, takes an equally uncompromising view.
Takayuchi Tsuchiya is a city councillor who wholeheartedly backs Governor Ishihara's new rule. "Singing Kimigayo will help promote a sense of national unity," he told me.
Open debate on divisive issues is strongly discouraged for fear it would disturb social harmony
In his view, Japan's hazy sense of national pride is to blame for its low profile in the world and for its weakness in the face of provocations, like North Korea's abduction of Japanese citizens.
Mr Takayuchi has no sympathy for rebel teachers. He dismisses them as communists who want to indoctrinate the children.
And what about the majority of Japanese who fall in between these militant guardians of Japan's history? It is almost impossible to know what they think.
The Japanese are fond of referring to their two sides - Honne and Tatemae - their true thoughts, and the face they show to the outside world.
Open debate on divisive issues is strongly discouraged for fear it would disturb social harmony.
The restored national anthem was first played at a 1999 remembrance ceremony
So there has been little public soul-searching about what went wrong with Japan before World War II.
While hard-liners on the left and right battle it out with their irreconcilable interpretations of the past, most Japanese seem happy to have drawn a line at 1945, and moved on.
They have a constitution written in haste by American occupiers, which technically bars Japan from even having an army, although its defence budget is now as big as Britain's.
They have an emperor whose status is vague. They allow right-wing politicians to make ludicrous denials of Japanese atrocities during the war - at great cost to Japan's relations with its Asian neighbours - all in the interest of avoiding uncomfortable issues.
This is why headmaster Toru Sato was so nervous that morning. Any hint that his teachers might have refused to respect the national anthem would not just get him in trouble with the city government, it would confront him, and the parents of his students, with an unresolved debate about their country they would prefer to avoid.
And that is why, even today after 60 years of unrivalled economic and scientific achievement, Japan still finds it hard to take its proper place in the world.
From Our Own Correspondent was broadcast on Saturday, 17 April, 2004 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.