The popular space man — who tweets and strums his guitar while flying kilometres above the planet's surface — joined a chorus of students in song before praising the art he said had an "enormous" impact on his life.
"Music opens doors and music stimulates the brain... It's a wonderful, applicable skill that only makes you a more capable human," he said.
Students from across the country tuned in via web link, with events planned in Ottawa, Vancouver and Winnipeg, among others.
Many joined Hadfield, the first Canadian to take command of the giant space laboratory, in singing the theme song for the Music Monday campaign, which he co-wrote with Barenaked Ladies frontman Ed Robertson.
In Toronto, students, teachers and fans packed into the Ontario Science Centre for a show that included several other performers, including the astronaut's brother Dave Hadfield.
A choir from the Chris Hadfield Public School in Milton, Ont., sang a song Dave Hadfield said he wrote for his brother's first trip to space.
Each musical number set off a wave of cheers and applause, but only the Music Monday tune — titled "I.S.S. (Is Somebody Singing)" — earned a standing ovation.
Hadfield, who is due to return from space next week, called the event "the very first Canada-wide, simultaneous space-to-Earth participatory broadcast" of its kind.
While fielding questions from students, he recalled buying his first record at the age of nine or 10 and said music has introduced him to strangers and helped him learn about other cultures.
It also taught him to improvise and be creative, skills that are crucial to his career, he added.
"The type of skills you develop in learning to play an instrument, with the discipline, learning to play in a group, with the harmony, and then the fundamental skills that come along with handling those things together — they're applicable whether you're an astronaut or really anybody trying to do anything," he told the eager crowd.
"So for a lot of different reasons, I think music makes me a better astronaut," he said.
In between questions, he fiddled with his guitar, seemingly to prevent it from floating away — a hazard of playing in space, he later said.
"When I try and play the guitar, it's not hanging on a strap, so as I play the guitar, it's like trying to play a guitar that's floating by," he told a girl who asked how the absence of gravity affected the instrument.
He drove the message home by signing off while hanging upside down, guitar in hand.
In the end, Hadfield's delivery captivated students as much as his message.
"You keep saying, 'Yeah, we're singing with Chris Hadfield in space' but once you actually saw him on the monitor and he was playing with his guitar and stuff, making it float, letting go of the microphone so it's just sitting there in front of his face, you're like, 'Wow, he's in space,'" said Steven Vlahos, 18, of Wexford Collegiate School for the Arts in Toronto.
Though he wasn't among the roughly 750,000 people following Hadfield's dispatches from space on Twitter, "I'm definitely going to start now," Vlahos said.
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