In an effort to improve student achievement at an urban high school, teachers and administrators developed a five-part, schoolwide vocabulary plan. Over four years, teachers provided students with increased opportunities to read, read to their students, developed content-specific vocabulary instruction, taught students academic words, and focused on five words each week with a common prefix, suffix, or root. Over the four years, student achievement in vocabulary and reading comprehension improved in significant ways, both on reading assessments and state achievement tests. (Contains 3 tables and 2 figures.)