However played out the high-school-coming-of-age may seem in movies, it still happens in real life. Well, isn’t that reason enough to have another go at a movie about it? What’s special about James Ponsoldt’s The Spectacular Now, adapted by Scott Neustadter and Michael H. Weber from Tim Tharp’s novel, is the power of undaunted sincerity. This is not an affected genre exercise; it’s a fond portrayal of living, fumbling individuals — wholeheartedly embodied by stars Miles Teller and Shailene Woodley, who couldn’t seem more winningly spontaneous. The proceedings are familiar: With graduation looming, an affable underachiever (Teller) strikes up a strong romantic bond with a bookish classmate (Woodley). She likes the sort of attention he offers, but lacks experience with it. He’s a genuine giver of love but a wounded and reluctant receiver. It matters that they’re both the children of single parents. Also, he drinks too much. And his ex (Brie Larson) is still in the picture; she dumped him, but mostly from disappointment that their mutual affection and attraction didn’t make a relationship sustainable. So what will? Ponsoldt’s emotional priorities seem mostly just right for so much fragile and lifelike adolescent intimacy, and Jess Hall’s caressing cinematography records it alertly. Whenever triteness encroaches, as it sometimes does, the actors — also including Kyle Chandler, uncomfortably good as a deadbeat dad — simply brush it away. This seems like a good moviemaking lesson for contrivance-addicts: Naturalism works if you work it.