Stephen Chbosky never intended to create a film series. But with the films “The Perks of Being a Wallflower,” “Wonder” and now “Dear Evan Hansen” under his belt, he jokes that he has made “The First Day of School Trilogy.”

Based on the Tony Award-winning musical, “Dear Evan Hansen” will open the Toronto International Film Festival on Sept. 9, and will be released in theaters on Sept. 24. It’s a bit of a departure for director Chbosky – it’s his first time helming a musical, though he adapted the screenplays for “Rent” and “Beauty and the Beast” – and it marks the first time he didn’t come aboard as writer, deferring duties to the play’s author, Steven Levenson. (Benj Pasek and Justin Paul, a.k.a. Pasek and Paul, wrote the music and lyrics.) But in many ways, it shares hallmarks with those others films, telling the story of an outsider with kindness and sensitivity.

Ben Platt reprises his Tony Award-winning role as Evan, a teenager with social anxiety, who unwittingly finds himself caught up in a lie when he is mistaken as a close friend of another teen, Connor, who commits suicide. In trying to comfort Connor’s family, Evan finds his deception going far deeper than intended.

You’re the opening night film at TIFF; what does that mean to you?

It means the world to me. I have a real soft spot in my heart for Toronto. The world premiere of “Perks” was there, and I will never forget it. So it feels like coming home to me.

What’s your history with “Dear Evan Hansen”? Did you see the musical first?

I saw the musical three years ago this summer. I was in I was in New York, dealing with my novel “Imaginary Friend.” I had a free night and I’d heard about the show but didn’t know what it was about. It was one of those instinctive things, a voice told me, “I should do this today.” So I went in completely blind and I loved it. I was blown away by the music, I thought the writing was superb. So I called my team and said, “Look I don’t know if they’re making a movie but if they do, I really want to meet with them.”

Do you usually pursue projects like that?

This is the first movie I ever chased as a director, really. Because I was not coming in as a writer. I revere authors and I wanted Steven and Pasek and Paul to approve of me. I wanted to meet them and go in and share my thoughts and if they disagree with my take, I didn’t want it. Because I was in service of this beautiful play they created, not the other way around. Luckily, they approved and we moved forward.

Had you been looking to direct a musical or was it more that this material spoke to you so strongly?

A bit of both. I love movie musicals and in the back of my head I thought it might be great to do one someday but I didn’t want to start with something that was a “Musical with a Capital M” – big, flashy numbers and set pieces and costumes. I wanted something intimidate, more like a drama with songs. So when I saw this, it was what I had been searching for.

How did it differ directing a musical; what were things you had to consider that maybe you never had before?

To me, live singing was a cornerstone of this particular movie. I had an instinct that the more matter of fact we could be about the music, the more the dialogue and lyrics are almost indistinguishable in how we approach them, that the tone would be more grounded and real. We’re dealing with real grief, real emotions; there really isn’t any fantasy. The difficulty with a musical usually is finding a reason to sing. And with some of the other musicals I’ve done and enjoyed, it’s usually performance or fantasy based; it’s inside a cabaret or it’s a Disney princess. But a dining room is different than a castle and a teenager’s bedroom is different than a cabaret. So we had to find the right way into each song.

And how did you do that?

Well it helps to have all these accomplished people like the writers and composers and [producer] Marc Platt. We talked a lot about the tone and we what each song is inherently about. Take “Waving Through a Window,” which opens the film. When we broke it down, we said, “This is a thought in his head. He’s not talking, he’s thinking.” So visually we approached it as him being separate from everybody. He goes to high school, he’s the outsider. It’s inspired by those amazing shots where you see one person in a crowd. We weren’t going to have him doing, like, “High School Musical” style choreography.

Again, with each song there was a dramatic reason to sing. And that’s what makes Pasek and Paul so special – there is no song for song’s sake. Everything is about moving forward with the story.

Were you involved with the conversations about some of the songs that were cut from the Broadway version?

Yes, we had many discussions about what each number did and what we needed. It was hard. The one song I love so much and was so sad to see go was “Does Anybody Have a Map?” It’s a great song and on stage, it works so well as an abstraction. It opens the show, we meet the families and the characters. But we felt the best way to tell the story was to start with Evan, start with “Waving Through a Window.” And then, when you meet Connor’s parents, they’re strangers to us. We’re really on Evan’s journey. It freed us up to meet all the characters through Evan. And it binds the audience to a way in Evan that is so valuable. These were the kinds of discussions we had a lot.

It looks like movie musicals are making a big comeback, there’s quite a few coming out this year.

What’s interesting is I was mixing “Dear Evan Hansen” in the same place where Lin-Manuel Miranda was mixing “Tick, Tick … Boom!” We had a lot of talks about Jonathan Larson because I adapted “Rent” and now Lin is directing the film adaptation of his first show and it was a really moving experience. Oh, and Steven Levenson adapted the screenplay for “Tick, Tick” so both of his films were on mixing stages at the same time in the same building. Just beautiful overlap.