The article explores the validity and reliability of an instrument for measuring for the School Environment (SE) among 3610 teachers in Medellín, Colombia during 2011. A multilevel exploratory factorial analysis established through 20 items that the instrument identifies four dimensions of SE on an individual level: communication between school and teachers, between teachers and parents, teacher involvement in school decisions, sense of security (respect-safeness) and academic expectations. At a group level, the same items measure a general dimension of SE. Based upon these analyses, the instrument produced a valid and reliable school environment measure that differentiates among schools.