Ten-year-old Claudia Hernandez, the daughter of Mexican immigrants, learned English in the schools here, and after her teacher gave her a dictionary as a gift, she studied at home, too, playing school with her younger brother. Claudia would be the teacher, she recalled, and together they would look up words. "I'd write out the definitions and memorize them," she said, "and my English just kept getting better." Claudia's recent certification as a fluent English speaker was a milestone for her and for her school, Butler Elementary, which like thousands of others across the nation has become eager to help students...