This study examined the effects of a multifaceted, metacognitive vocabulary intervention on the reading comprehension and vocabulary achievement of fifth-grade children in one of California's lowest performing Title I schools. Instruction was comprehensive, designed to facilitate encoding of student-selected words, mastery of clarifying strategies, and executive control of strategies that maximize word-learning proficiency. Strong gains in reading comprehension and vocabulary achievement and increased metacognitive skills were documented following the 12-week vocabulary intervention. Comparisons of Title I students' scores and those of students in an above-average-performing school revealed large, significant differences before the intervention and small, nonsignificant differences following the intervention, suggesting a narrowing of the achievement gap.