Relative age effects occur when older and younger students are peers in the same classroom. Previous research in this field has shown that older children have higher academic achievement compared to the youngest children in the same grade. This study examined the effects of separating kindergarten students into classes based solely on age. The groups of students were compared to each other and to a control group of students who were not in classes dependent on age. The results show that while older students still score higher than younger students by the end of the year, the students in the youngest classroom made larger gains in achievement during the year in math and reading.