To address the nations' ongoing interest in student achievement, some researchers have focused on the effect of block scheduling--a model in which students take fewer classes for longer periods of time. Although block scheduling has demonstrated its viability in high schools, little research has explored its effect at the middle level. Because the middle level years are often marked by a decline in student achievement, particularly during the transitional year when students move from elementary school to sixth-grade, the current study was conducted. Results revealed significant increases in the mathematics achievement scores of sixth-grade students' enrolled in five middle level schools that transitioned from traditional to block schedules. Characteristics of block scheduling that may have accounted for these outcomes and recommendations for future research are discussed.