This novel diagnostic tool is based on students' performance at second level and the subjects they studied, with their interests and resulting personality types from Holland's Interest Inventory. The intent is to provide an accurate predictor of student performance and in doing so also offer a detailed insight into the influences on student learning outcomes and retention. A greater understanding of the factors influencing student performance can lead to better-informed teaching and learning strategies, the appropriate application of additional support and, as a result, enhanced student learning outcomes and retention. The Self-Directed Search (SDS) interest inventory used in this research is widely regarded is the most contemporary and extensive test available.