Educators have generally believed that foreign language instruction should begin in kindergarten or earlier to promote optimum oral language development (e.g., Abbott, 1998; Curtain & Dahlberg, 2010; Rhodes & Pufahl, 2010; Rosenbusch, 1991; Swender & Duncan, 1998). This article describes two Spanish programs in the Westport (Connecticut) Public Schools district: their new, long-sequence K-8 program and the short-sequence Grade 5-8 program it replaced. A five-year study examined students' oral and listening comprehension proficiency levels in each program at the end of Grades 5 and 8. Results at these grade levels were compared to determine program effectiveness. Students who began in kindergarten attained statistically higher proficiency levels than those who began in Grade 5. This longitudinal study strongly supports school-based language instruction beginning in kindergarten. (Contains 7 tables.)