In “Boyhood,” Mason (played by Ellar Coltrane) ages 12 years over the course of the film, which was shot between 2002 and 2013. (IFC Films)

The shooting schedule for “Boyhood” wasn’t bad. The entire film was shot in around 40 days. It’s just that it took nearly 12 years. 

Richard Linklater, director of films like “Dazed and Confused,” “Before Sunrise” and “Bernie,” has pulled off his most extraordinary experiment yet. He wanted to tell the story of an entire childhood but didn’t want to recast his central actor as the character aged. So in “Boyhood,” out locally Friday, Ellar Coltrane plays Mason from ages 6 to 18 — not through the magic of CGI, but because shooting started in 2002 and wrapped last October, with the cast reconvening for a few days each year in between.

It was a huge gamble for a lot of reasons, but Linklater, who also wrote the film, says he always knew it would all work out. 

“I had some strange confidence in my ability to work with whatever reality threw at me,” he says. So he didn’t worry that, for instance, his lead actor would get hit by a bus midway or even that Coltrane would be unable to pull off the later, more emotionally resonant scenes. 

“He certainly didn’t suck [at acting] when he was young,” Linklater says. “Plus, at some point, probably by high school, that character is sort of meshing together with him to some degree.”

While the film concentrates on Mason and, to a lesser degree, his sister Samantha (played by the director’s daughter Lorelei), it’s not all about the kids. The parents (Patricia Arquette and Ethan Hawke) get their own compelling, if peripheral, stories. “I knew where they were going even more specifically than the kids,” Linklater says. “That was all kind of mapped out in advance,” often with the help of the two actors. “That was the fun, collaborative nature of the film. We had a year to think about what would come next.”

Linklater knows people will come to the movie just to see how well he pulls this off — as well as to experience watching characters age 12 years in 2½ hours. 

“It’s clearly something no one’s done before, and that’s good news,” he says. “The other good news is that they will see how that was a storytelling device. It wasn’t a gimmick. They’ll go in on a conceptual level and come out thinking, ‘Wow, I’ve felt things I haven’t felt before.’ ” Kristen Page-Kirby (Express)

Want more film?

‘Life Itself’ is the story of Roger Ebert & dad & me

Five documentaries you should see before you see “Korengal”

“The Railway Man” doesn’t quite get the gray areas of PTSD

“The Fault in Our Stars” shows the blunt force of cancer