Sweetness pervades this adaptation of a Wired article, in which four undocumented Hispanic Arizona high schoolers form a ragtag club to enter a college robotics contest. In the movie version, they have guidance from a hesitantly invested substitute teacher played by George Lopez. Call it a sign of the times that it’s so rousing to see these scrappy bot-builders hold their own among complacent, well-funded, mostly lily-white brainiacs. (Revenge on the nerds?) But just because Spare Parts tells the true-enough story of at least one literal poster child for Obama-style immigration reform doesn’t mean it won’t also sit well with a traditional family-values crowd: As it happens, the club’s semi-reluctant founder is a straight-arrow ROTC kid (Carlos PenaVega) who can’t join the Army without papers and needs some other productive thing to do. So this can be a tame and sentimental tale of up-by-bootstraps underdog triumph after all. As directed by Sean McNamara, from Elissa Matsueda’s script, scenes make such short work of their straightforward emotional intentions that the movie sometimes seems almost like an abridgment of or commercial for itself. But Lopez sneaks his humor in gently, remaining a faithful servant of the story and its hopeful message. Jamie Lee Curtis, as the school principal, adds warmth, and Marisa Tomei, as a fellow teacher, undoes many clichés before they can even happen.