This paper explores the argumentation ability of ten science teachers in two South African schools on opposite ends of the resource spectrum. Toulmin's model is used to analyse individual contributions in six group discussions. The findings show that levels of argumentation improve with teachers' involvement in the development of teaching resources and the closeness of the argumentation task. The nature of the arguments is permeated by inclusiveness, thus precluding the use of rebuttals, traditionally a requirement for high-quality arguments. Based on the "ubuntu" worldview, a model of inclusive argumentation is proposed with implication for teaching and a scheme of assessable levels of argumentation.