This study focused on the differences in outcomes for three academic years of 10th grade students grouped into standard and advanced classes compared to three academic years of students grouped into heterogeneous academies. A chi-square analysis indicated that the mixed-ability group outperformed the standard/advanced grouped students on reading, language, and social studies exit exam subtests in the majority of disaggregated subgroups. Results revealed that the mixed-ability grouping intervention was especially effective for females and students from lower socioeconomic levels. Additional descriptive and qualitative data supported the quantitative findings through patterns and themes consistent with instructional and cultural school improvement. The findings are congruent with the research on the benefits of academies and small learning communities on student motivation and achievement. Interviews of academy teachers further supported these findings and the relevant research by revealing that restructuring the school day alone will not necessarily increase student motivation and achievement. The restructuring must be accompanied by motivational strategies, professional development, improved teacher practices, and administrative support.