The purpose of present research was to study the current and optimal status of teaching environment at high schools in Iran with emphasis on curriculum experts and teachers' viewpoints. Research method was mixed method. In the qualitative part, experts' viewpoints were gathered through a semi-structured interview. In the quantitative part, 258 high school teachers were selected randomly as statistical sample and a researcher-made questionnaire was distributed among them to collect data. Content validity was used to determine the questionnaire validity, and its reliability was calculated at 0.90, using Cronbach at alpha coefficient. Findings showed that, according to experts' viewpoints, status of teaching environment at high schools is not desirable. Also, findings suggest that the best teaching method for environment in Iran is a blended-electronic, project-oriented, teaching practical skills in open spaces. Iranian teachers chose teaching methods to teach environmental not only to promote their knowledge but also affect the attitude and skills of environmental protection and creating environmental conduct.