For the most part, the proper length for a Sundance Film Festival documentary is between 80 and 95 minutes. There is almost literally no subject matter that I don't have an hour-and-a-half of interest in. I just watched "The Machine Which Makes Everything Disappear," a 97-minute documentary from Georgia -- the former Soviet republic, not the home of the Falcons -- in which nothing at all happened, but it was still worthy, because it offered a series of vignettes from a national and a culture that are totally foreign to me. The same is equally true of docs about cows, killer whales and several variations on economic inequality themes.
"American Promise," already set to air on PBS' "POV," has a running time of just over 140 minutes. It isn't just the longest documentary in either the US or World competition, but it's the only doc in either competition to top two hours. 
"American Promise" has many lessons -- It runs an intellectual gamut -- but its biggest lesson is probably that there actually isn't a "proper" length for any documentary. Spanning over a decade in the lives of two kids and two families, "American Promise" is substantive and emotionally epic, one of the most thoughtful and nourishing films I've seen for this year's Festival. 
Joe Brewster and Michele Stephenson's documentary breaks the peculiar B-range grading logjam I've been in since hitting Sundance. It's a film that should have people talking, both in Park City and, in a few months, in living rooms and classrooms.
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Because of its longitudinal study structure and its use of maturing children to touch on issues of race and class in contemporary America, it's tempting to think of "American Promise" as "Hoop Dreams" without the hoops. That's a comparison worth avoiding, both because "Hoop Dreams" is in a class by itself and because "American Promise" actually includes a smattering of basketball, albeit nowhere near the forefront. 
"American Promise" begins in 1999 when Brewster and Stephenson decided to send their five-year-old son Idris to begin kindergarten at the Dalton School, which chyrons tell me is an astoundingly prestigious prep school, sending 31 percent of its student body to the Ivy League, M.I.T. or Stanford. Idris is joined by best friend Seun, as the kids and their parents are taking advantage of Dalton's efforts to expand the diversity of its student body. They also decided to follow Idris and Seun -- plus several other kids who dropped out of the project, as often happens with longitudinal study documentaries -- with cameras to showcase the anticipated culture shock.
It's an interesting filmmaking and sociological experiment both in how it reflects on Idris and Seun, but what it says about the parents who choose to transform their kids into guinea pigs. It's to Brewster and Stephenson's credit that while they're not quite as central to the film as Idris, not only are they very present, but they're also not embarrassed to potentially look bad. Brewster in particular alternates between being a caring father and a high-pressure tyrant in a way that's fairly normal, but also could have been dodged if the co-director had felt any self-consciousness. 
Over the 12-year educational journey, Idris and Seun grow up and develop in exactly the ways that good drama would tend to dictate. Both have academic struggles and face the option of leaving Dalton. Both battle learning disabilities and the need to be properly diagnosed. Both face the possibility that they are being judged by teachers and administrators on criteria weighted by race and gender issues. Both deal with the challenges of assimilating into a majority white culture and then both deal with the ramifications of being seen as too white. These are the same issues that their parents also have to contemplate, as they wonder whether or not they did right by their sons, as Idris and Seun also go through normal rites of passage like varying popularity and dating and the looming prospect of college. "American Promise" has all of the generalities that any parent will find familiar, with specificities stemming from the public/private school divide as well as society's expectations of and involuntary responses to black masculinity. There's a lot to chew on.
There's always a dice-rolling side to documentaries like this. Idris and Seun both could have excelled in classes, been the coolest kids in their school, matured preternaturally and gotten into Harvard and Brewster and Stephenson would have been left scrambling to get heft out of their 12 years of footage. Fortunately for the documentary, if not for Idris and Seun, the two subjects go from fairly normal kids to fairly normal teens. Idris is prone to temper tantrums, he's shy with girls and he's undersized to play basketball. Seun's family issues pile up distressingly. 
And, throughout, the bottom line message of the documentary is constantly shifting. There are a couple moments where it feels like simple answers are being suggested, but there is a more complicated meditation here. It's not as simple as "Kids learn better when they're in high-achieving and diverse environments" nor "Go to school with people like you and you'll be a better student." Sometimes "bad" parenting yields positive results and sometimes "nurturing" leads to something counter-intuitive. In "American Promises," choices have consequences, but institutional impediments can be just as powerful. 
Many Sundance movies make strong and convincing cases, but they eventually lead to single homogenous conclusions. If you watch "Blackfish," you come out angry with Seaworld. You leave "Pussy Riot - A Punk Prayer" outraged at the state of justice in Russia. In contrast, "American Promise" doesn't force viewers to any one conclusion and could open things up for debate, without necessarily being polarizing. Oh and it's also an enjoyable, frequently funny, sometimes sad film. Engaging to both the mind and the heart? Yeah, "American Promises" is one of the best Sundance movies I've seen this year.
A long-time member of the TCA Board and a longer-time blogger of "American Idol," Dan Fienberg writes about TV, except for when he writes about movies or sometimes writes about the Red Sox. But never music. He would sound stupid talking about music.