Knowing about teacher perceptions contributes to the understanding of teachers' attitudes toward the behavior of their students. We evaluated the perceptions of 501 teachers about the genetic and environmental influences on behaviors considered relevant to the educational environment using an original questionnaire from the United Kingdom, adapted to the Portuguese language of Brazil. We found that the teachers attributed genetic and environmental influences evenly regarding personality and learning difficulties; greater genetic influence on intelligence and mental illness; and greater environmental influence on behavioral problems. Most teachers stated that having a student with genetically influenced learning difficulties would affect their method of instructing them.