Previous studies on the influence of mixed groupings within preschool classrooms have indicated positive effects on childrens development. This study extended earlier findings to determine the effects of socioeconomic diversity within the classroom on the language, cognitive and social-emotional development of preschool children of low-income backgrounds. Twenty-seven preschool children were enrolled in two classrooms in a private university's child development center. Twenty of the 27 enrolled were from low-income backgrounds. The children were tested to determine a baseline measure of their language, cognitive and social-emotional skills. Classroom observations of the children's language behavior were coded. Post-testing was done at the conclusion of the school year to determine growth in language, cognitive and social-emotional skills. Differences in language usage and social-emotional development were observed. These results suggest that mixed income grouping as well as teacher interactions influence language and social-emotional development of children from low-income backgrounds.