The purpose of this mixed methods study was to investigate, describe, and understand the current provision of music education in post-primary (secondary) schools in Ireland as reported by school principals. Data included a large-scale national survey (n = 410) with a 59% response rate and 17 follow-up face-to-face interviews. The findings revealed how music instruction was provided for, in addition to principals’ expectations of music programs and music teachers. Using a systems ecological framework, factors influencing principals’ support of music in schools were also identified. It was found that music education practices are inconsistent throughout post-primary schools to the point of insidious decline in many schools, as principals are not all exercising the autonomy granted to them to develop equitable curricula and music-making opportunities. Music programs tended to exist less frequently in all-boys’ schools and in smaller schools. Based on the degree to which principals demonstrated commitment to the implementation of music in their curricula, three distinct types of principals emerged and were categorized as the Progressives (managing schools with exemplar music programs), the Maintainers (struggling to develop music in their schools) and the Disinclined (unwilling or unable to implement music in their schools). The majority of principals articulated high expectations for music in the school and communicated the importance of music in the curriculum for aesthetic, utilitarian, and extra-curricular benefits. However, principals’ glowing endorsements of music education did not necessarily translate into action and implementation. Principals highlighted that the vibrancy of a music program is contingent upon recruiting competent, committed, and positive music teachers who act as evangelists for music. The absence of a clear and cohesive framework for principals from centralized government, the Department of Education and Skills (DES), is inimical to the development of music in schools; whereas creative funding, scheduling, and recruitment strategies facilitate the support of music in schools. The primary recommendation resulting from this study is that a pyramidal governance structure is required so that the DES takes a stronger leadership role by developing relevant and cogent music education guidelines for principals and music teachers.