Abstract
Out-of-field (OOF) mathematics teaching is complex and context-dependent, particularly where formal qualifications do not adequately reflect teachers’ preparedness. Drawing on a longitudinal professional development (PD) programme for junior secondary mathematics teachers in South African schools serving low-income communities, this paper broadens the conceptualisation of OOF teaching and distils principles for context-relevant PD. We describe a sustained mathematics-for-teaching course that prioritised mathematical knowledge while explicitly mediating mathematics teaching practices. Teacher assessments and a quasi-experimental learner study showed significant gains in teachers’ mathematical knowledge and modest but significant gains in learner attainment, with indications that learner impact may be delayed. These findings support extending OOF beyond formal qualification criteria to include teachers who self-identify as underprepared. We propose principles for sustained, context-conscious PD that works “with the grain” of existing practices, bringing evidence from the Global South to a predominantly Global North literature.