Within initial teacher education there is increasing pressure to enhance the use of assessment data to support students to improve their knowledge and skills, and to determine what standards they meet upon graduation. For such data to be useful, both programme designers and students require meaningful and comprehensive assessment reports on students' performance. However, current reporting formats, based on percentages, are inadequate for providing meaningful qualitative information on students' mathematics proficiency and, therefore, are unlikely to be used for interventions to improve teaching and enhance learning. This article proposes standard setting as an approach to reporting the assessment results in formats that are meaningful for decision-making and efficacious in subsequent interventions. Mathematics tests, developed through the Primary Teacher Education (PrimTEd) project, were administered electronically on a convenient sample of first-year and fourth-year PrimTEd students (N = 1 377). The data were analysed using traditional descriptive statistical analysis and the Objective Standard Setting method. The two reporting formats -- one using a percentage score and the other using standards-based performance levels -- were then compared. The study identified important distinguishing features of students' mathematical proficiency from the two reporting formats, and makes important findings on the specific knowledge and skills that students in South African initial teacher education programmes demonstrate. We conclude that reporting assessment results in standards-based formats facilitates differentiated interventions to meet students' learning needs. Furthermore, this approach holds good prospects for benchmarking performance across universities and for monitoring national standards.