This article reports on the development of an interpersonal measure for students with additional learning needs. A questionnaire and learning continuum were constructed using a methodology devised by Griffin (2007a) for creating criterion-referenced frameworks. Teachers reported on 1619 students, ranging in age from 3 to 18 years. Analysis of the data, using item response modelling, found the questionnaire was able to measure interpersonal capacity reliably over a large ability range. The interpersonal domain is an imprecise and multifaceted area, so how teachers should support the learning needs of students within it is not always apparent. The devised measures offer the prospect of a more systematic and evidence-based approach to educating students within this domain.