This study has the primary objective to find out the importance and usefulness of teaching and learning materials for overcrowded or large classes. The research area is in Arumeru District, Tanzania. Social Constructivism Theory has been used for this study. Mixed method approach has been deployed. Sample consists of four heads of schools, fortyeight faculties, and hundred and sixty students from four public secondary schools. Various data collection instruments have been used. Some of them are questionnaires, observation guide and in-depth interview guides. SPSS has been used for analysis. The study revealed that teachers in large class size considered teaching and learning materials as key to academic performance. The study also revealed that teaching learning materials has direct association with student's performance. Some recommendations related to government policies also have been provided during this study.