"Everyone was afraid that they'd be drafted to a war they didn't even know much about," he says.
Kan later became a solicitor in Canada and Hong Kong, but the idea of Teach-In never left his mind. Last year, he started his first Teach-In-inspired youth forum, Teen Talk, in Hong Kong.
Teen Talk, organised by the Law Society of Hong Kong, attracted about 1,400 secondary school students last year. And this year, as many as 2,200 students have signed up.
Kan sees Teen Talk as a platform for teenagers to speak freely. Last year, students shared their opinions after watching a drama, staged by young lawyers, about compensated dating and cyber bullying. This year, the focus is on morality. Students will be watching three brain-teasing videos - and one of them is about cannibalism. "It's always in extreme cases that your moral values will be put to the test," Kan says.
Although students will come across challenging taboos, Kan is confident that these topics will work well without crossing any lines.
"These are just points of departure, not real issues," Kan says.
Kan's decision to make morality this year's theme is no coincidence. A survey conducted during last year's event found that half of the 1,400 participants felt the morals of youth were declining.
Kan found it shocking to hear that 20 per cent of the participants would do whatever it took, legally or illegally, to make money unless it involved something really terrible.
Kan (above) will use this year's Teen Talk to impart his ABC to students: A for awareness, B for broadening and C for critical thinking.
Genevieve Yue Hon-jun from Marymount Secondary School, who attended last year's event, says she had never thought so deeply about cyber bullying. "There were victims in the US who actually died because of cyber bullying," she says.
Nicole Chan Fong-yuen, also from Marymount, says she found last year's event was like a bridge bringing the worlds of adults and teenagers closer. In a sharing session, two or three representatives from the Law Society of Hong Kong would moderate the discussion in each eight-person group.
"Before this event, I did not know that lawyers could be so close to students and willing to tell us what they think," Nicole says. "The talk made me feel that they are very active in educating the younger generation."
Katriana Cheung Wai-yi, who will be participating for the first time this year, says events like this are very important because students nowadays rarely read the news and don't know how to communicate with others. Teen Talk encourages them to read and share.
One of the key elements of Teach-In was music. To keep that element of the original intact, Kan has also arranged for Canto-pop singer Ken Hung Cheuk-lap to sing on the day.
Kan jokes there is definitely room for improvement, though. Last year, performing guest Vincy Chan Ka-yan, or Wing Yee as she is popularly known, caused chaos when she left the stage.
"This year, Ken will have to stay on stage at all times," he says.
Catering was also a problem last year as there was a shortage of food. "I'll make sure there will be enough food for all the boys this time," Kan laughs.
Teen Talk takes place tomorrow at AsiaWorld-Expo. Registration has closed, so look out for details of next year's event.