The authors examined the conditions that promote or discourage engagement in the classroom among kindergarten students. Engagement included learning behaviors (on-task behavior) and pro- and antisocial behavior. The authors examined 3 policy-manipulable features of kindergarten classrooms: (a) whether the class met for a half day or full day, (b) class size, and (c) whether a teacher aide was present in the classroom. Data for the study comprised a national sample of kindergarten students, their teachers and schools, from the Early Childhood Longitudinal Study, U.S. Department of Education. Measures of engagement were the teachers' overall ratings of classroom behavior and their ratings of individual students on academic and social engagement measures. Ratings of class behavior were related significantly to class scheduling (students in full-day kindergartens rated the poorest) and to class size (students in small classes rated as better behaved than those in large classes). Ratings of student behavior were not consistently related to class scheduling or to class size. No behavior rating was significantly related to the presence of a teacher aide: this finding adds to a plethora of negative results regarding classroom aides. Results are discussed in terms of the disjuncture between teachers' ratings of individual students, which yielded relatively little interclass variation, and global ratings of entire classes. Valid measures of class-level outcomes are needed for educators to assess class-level practices that include organizational policies and teacher approaches to instruction.Key words: classroom organization and engagement, early childhood longitudinal study, kindergarten students' behavior