“We have ideas, and they need to be implemented,” says a teenage girl named Marissa. Marissa is one of six subjects in Margaret Lampert’s new documentary short film, “The Art of Growing Up,” which offers an evocative glimpse into the hearts and minds of today’s youth. Divided into five loosely themed chapters, the film has all the Lampert signatures—lush lighting, bright faces, abiding authenticity—alongside the elements of sound and movement.