Katie Dellamaggiore's sweet, winning documentary spends one year with the chess team at Intermediate School 318, an inner-city junior high in Brooklyn, where despite a 70 percent poverty rate, the kids, grades 6-9, routinely win national championships. The secret is an extraordinarily supportive administration and a crackerjack chess teacher, Elizabeth Spiegel, who devotes her life to teaching students what to do after P-K4. And the I.S. 318 team? A delightfully motley, vulnerable, multicultural bunch, whose addiction to chess has allowed them higher aspirations for top high schools and, eventually, college and careers. You will root for them like crazy when they travel far from Brooklyn to compete.