Instrument development is an important step towards unlocking the analytical power of teacher attitudes and beliefs towards Computer Science (CS). Teacher dispositions have strong empirical and theoretical ties to teacher motivation, professional choices, and classroom practices. To determine consensus desirable attitudes and beliefs, we analyzed 17 key documents produced by 12 national and international organizations associated with CS and the CS education reform movement. An analysis of 98 relevant coded segments yielded four dispositional targets: an equity orientation, a teacher growth mindset, and key beliefs regarding (career) outcomes and epistemology of CS. Statements crafted for these targets as well as self-efficacy were reviewed through an expert panel (N = 5) and a pilot study (N = 22) before the T-ABC was administered to elementary teachers in a large grant-funded outreach project (N = 772). Psychometric analysis demonstrates high reliability (Cronbach's alpha = 0.89) and satisfactory extraction and loading onto a three factor model, with CS beliefs, growth mindset, and self-efficacy as major factors. Identification and measurements of teacher dispositions enables further analysis of how teacher beliefs may support or hinder effective practice in CS instruction, how teacher populations may differ, and how identified dispositions may change with exposure to various CS learning experiences.