This study was conducted to compare the effects of classroom setting on student performance and teachers’ sense of efficacy. In this study, student performance on the Missouri Assessment Program grade-level assessments at the third and fourth-grade levels was utilized to compare the multiage team-taught classroom setting versus single-age classroom setting. The teachers’ sense of efficacy on the Teachers’ Sense of Efficacy Scale (TSES) survey was also analyzed to compare multiage team-taught classroom setting and single-age classroom setting. The data were interpreted to support that students in multiage team-taught classroom settings outperformed similar age students in single-age classroom settings on the MAP assessment at the third and fourth-grade levels in both English language arts and mathematics. The third-grade students showed a significant difference in assessment scores in favor of the multiage team-taught classroom setting. The fourth-grade students showed a difference in favor of the multiage team-taught classroom setting, but not at a significant level. The results from the teacher survey could be interpreted to establish that teachers in the multiage team-taught classroom setting rated themselves higher on the TSES than teachers in a single-age classroom setting. The teachers in a multiage team-taught setting rated their beliefs significantly higher on all three subscale scores of the TSES compared to the teachers in the single-age classroom setting. The results from this study supported the use of the multiage team-taught classroom setting at the third and fourth-grade levels.