The general education teacher has the greatest influence on a student's success in school, and a teacher's attitude towards inclusion is a major factor in determining whether inclusion will be successful. The ATTAS-mm is a 9-item scale with strong reliability and validity. The three subscales: believing all students can succeed in general education classrooms (cognitive), developing personal and professional relationships (affective), and creating an accepting environment for all students to learn (behavioral) explain nearly 80% of the variance in scores. The unstandardized Cronbach alpha for the entire ATTAS-mm scale was 0.83. The three subscales also demonstrated acceptable reliability values (Cognitive, 0.72; Affective, 0.93; Behavioral, 0.84). The theoretical underpinning of the scale, development of the scale, and technical details are explained. Additionally, scoring procedures, scale itself and information regarding permission to reproduce or administer the scale are included. With strong internal reliability and validity established through a panel of experts and alignment with cognitive psychology literature, the ATTAS-mm was determined to be a valid and reliable instrument for measuring the attitudes towards teaching all students. Attitudes Towards Teaching All Students: ATTAS-mm is appended. (Contains 5 tables.)