Evidence-informed collaborative inquiry is central to the improvement of teaching and learning for diverse students. This research investigated the impact of a professional learning intervention on the improvement of social studies teachers' practice, and their students' learning. Data were gathered from 26 primary and secondary teachers before, during, and after a year-long research and development project. Analysis of interviews, observation notes, teachers' reports, and reflective journals revealed how "both" engagement with outcomes-linked evidence and collaborative inquiry supported and challenged teachers to improve their classroom practice, and positively impacted on a range of outcomes for their learners. We illustrate this through two vignettes of teachers' inquiries. (Contains 1 figure and 12 notes.)