updated 07/14/2014 AT 11:15 AM ET
•originally published 07/13/2014 AT 7:00 PM ET
Talk about the role of a lifetime – in what looks to be shaping up into one of the movies of the year.
Ellar Coltrane was just 6 years old when he began filming Boyhood. And now, just a month before his 20th birthday, audiences are watching Coltrane grow up before their eyes in director Richard Linklater’s film, which has been 12 years in the making.
“It was a very transformative thing,” Coltrane tells PEOPLE of getting to grow up alongside his character, Mason. “You can look in the mirror, but you can’t really see yourself changing – or how you don’t change – over the years. It is very bizarre to see it all organized [on screen].”
Boyhood follows Mason, his mother (Patricia Arquette), father (Ethan Hawke) and sister (Linklater’s daughter Lorelei) as the child ages from a young boy into a sensitive, artistic high school graduate.
One of the Year’s Best
Critical reaction (see below) has been excellent and contributed to an impressive opening weekend box-office. In the specialty film market, Boyhood, which opened Friday, set a second-best record for the year, trailing only The Grand Budapest Hotel.
Time, praising the work as “a thrilling epic of ordinary life,” noted, “Coltrane has the gift of visible introspection” – remarkable for his tender age.
“It just became very much of a collaboration,” Coltrane says of growing close with his costars and director as they filmed in small spurts over the years. “When you’re young, you’re kind of just along for the ride, I guess. But over time, we became more of partners creating something.”
Coltrane doesn’t remember much about his initial audition so many years ago, but he does recall it taking a long time.
“[Richard] didn’t have a script written, so there were no scenes to read,” he says. “It was just having conversations and getting to know each other.”
Because there was no long-term plan for the storyline, Coltrane says Linklater would occasionally pull from the actor’s real life for inspiration.
“He would keep in touch with me. He would call me on the phone or take me out to lunch pretty often,” says Coltrane, who has had small roles in a handful of independent films, including Linklater’s Fast Food Nation. “There was a lot of me that is reflected in the character, but he also has his own life.”
Coltrane went to a theater camp or two when he was younger but says the idea of doing live theater “scares” him. He admits he went through periods of time where acting was not a priority. Like his character, he also has a passion for photography.
But with his first starring role under his belt, Coltrane is grateful for the experience and looks forward to continuing to pursue acting close to home in Austin, Texas, where some of the movie was filmed.
“I don’t really see myself leaving home anytime soon, really,” says Coltrane, who was home-schooled. “I want to go to [college], so I guess that is next. I’m interested in all kinds of art. But I’ve got to figure out what to do after that.”
One thing he’s sure about: He’d be in for a sequel. Manhood – in theaters in 2026?
“If [Richard] was going to make it,” says Coltrane, “I would be up for it.”
Additional reporting by STEPHEN M. SILVERMAN