Abstract The Highly Accomplished and Lead Teacher (HALT) Certification process introduced in Australia in 2012 was designed to recognise expert teachers, to encourage them to continue to influence and impact their students and colleagues through their exemplary classroom practice. Expert teachers prepare evidence of their impactful practices, and have this evidence evaluated through a National Certifying Authority. HALTs are a relatively new role in Australian education, and little is known about their impact in schools, or the potential for their ongoing role as middle leaders in schools. This paper analyses the experiences of HALT teachers who had been certified by Independent Schools Queensland (ISQ) in 2018, and what impact they recognised they were having in the schools who supported them through their certification process. Impact is theorised as a temporal, reflexive narrative. Data were gathered in a cascading evaluative process through portfolio analysis, interviews with nationally certified teachers, school-based mentors and school leaders and a survey about their teacher and middle leader efficacy. The process of applying for HALT Certification had significant positive personal impact for the teachers, their students, their colleagues in their school and for some, beyond their school. The recognition of impact as a temporal narrative with distinct genres, and the concept of HALT teachers as middle leaders may point to new avenues of supporting applicants and to potential benefits for schools to encourage teachers to consider national certification.