This paper focuses on results from testing for the Mathematics Intervention program. To determine whether students participating in the Grade 1 Intervention program maintained the progress made during the program, students were also tested when in Grade 3 or Grade 4. The main aim of this testing was to determine whether an intervention program at Grade 1 can assist students to develop flexibility in their mathematical thinking, enabling them to develop their own strategies and to be less reliant on rules and procedures. The assessment method used for the testing at both Grade 3 and Grade 4 and at the initial Grade 1 were based on research. The theoretical underpinning of the testing will be discussed briefly. A case study of one of the students involved in both sets of testing will be presented to allow some longitudinal data to be presented.