Bearing traces of Huck Finn and Antoine Doinel, Low Tide’s nameless adolescent hero (Daniel Blanchard) runs errands and cares for his substance-abusing mother (Melissa McKinney). Roberto Minervini’s second feature casts nonprofessionals to magnificently truthful effect, and the writer/director demonstrates his characteristic sensitivity for small Texas towns and their resilient denizens. Blanchard is seldom off-screen, as Minervini follows him on his “rounds” from the nursing home where his mother works to a slaughterhouse, but also to the river to catch frogs and fish. Minervini does not mute the hardships of his protagonist’s life, nor does he deny him the right to be 12 years old.