Documentarians Parker Hill and Isabel Bethencourt follow around a group of Texas trailer park kids for a year in “Cusp,” an eye-opening vérité film about the angst, struggle, and heartbreak of being a teenager. It’s a shame that the film’s subjects aren’t very interesting, because there are some very disturbing and provocative discussions and events shown on camera that detail the sad reality for many young women in America today. One thing this film does is reiterate the fact that parental responsibility is vital to raising strong, confident adults. Most of these girls don’t have adequate s...