Māori language education settings have resulted in teachers requiring efficient ways to identify the oral Māori language proficiency of students at the beginning of Māori-immersion schooling and throughout their participation as the basis for students’ ongoing learning. Accordingly, three assessment tools were developed using understandings from sociocultural perspectives on human learning that emphasise the importance of the responsive social and cultural contexts in which learning takes place. The researchers aimed to promote culturally responsive contexts in which students would talk about topics of interest. Once the tools and processes were found to have cultural legitimacy, further trials in a number of settings tested two of the assessments for measurement reliability and validity. This paper introduces the assessment tools and discusses the establishment of cultural legitimacy. It then discusses assessing the reliability of the tools using test–retest and internal consistency evidence, and assessing the tools for content validity.