Teen movies, especially those made using a rearview mirror, have become essential to generational mythology. I can’t speak for how accurately George Lucas’s “American Graffiti” captured what it was like to be a teen-ager in the early sixties, nor can I fairly assess the portrait of an early-two-thousands high-school experience provided by Greta Gerwig’s “Lady Bird.” But I can vouch for “Dazed and Confused,” which not only nails the clothes, hair, music, and cars of the period but also the laissez-faire vibe—the way parents and other authority figures, who had divorce and EST to deal with, seemed checked out, and kids were left to stumble through adolescence on their own.