Teachers use student grouping to reduce the complexities of the classroom. Grouping has been credited with making behavior more predictable, improving interpersonal skills, and making instruction easier by increasing homogeneity. Research suggests that teachers' grouping decisions are influenced by characteristics of the student, the teacher, the task, and the environment. Research on grouping has centered on elementary classes, with little investigation of secondary classes. The purpose of this study was to describe the influences on secondary laboratory teachers' grouping decisions in a naturally occurring secondary school setting.