The purpose of this study is to examine the relationship between school ethical climate, organizational citizenship behavior and social loafing. The study participants included 878 teachers, 50 principals and 50 school counselors from 50 primary schools. The data analysis was based on multilevel SEM. The findings indicate different behavioral mechanisms between the individual and the group levels among teachers. A positive relation was found between personal organizational citizenship behavior and group organizational citizenship behavior, as well as a negative relation between group organizational citizenship behavior and social loafing. In practice, school leaders should encourage workgroups for maximizing school effectiveness.