The Say-All-Fast-Minute-Every-Day-Shuffled (SAFMEDS) strategy promotes fast and accurate recall. The existing literature suggests that the strategy can help learners improve academic outcomes. Through a cluster randomized controlled trial, we assessed the impact of implementation support on children's mathematics outcomes during a teacher-led SAFMEDS intervention. Following training and prior to baseline assessments, we randomly allocated schools to receive either no (n = 31) or ongoing (n = 33) support from a researcher. Support consisted of three "in-situ" visits and email contact. Assessors remained blind to the condition of the schools throughout. We analyzed the outcomes of children (n[subscript Support] = 294, n[subscript NoSupport] = 281) using a multi-level mixed-effects model; accounting for the children nested within schools. The results suggest that implementation support has a small effect on children's fluency of arithmetic facts (Mathematics Fluency and Calculation Tests (MFaCTs): Grades 1-2, d = 0.23, 95% CI: 0.06-0.40; MFaCTs: Grades 3-5, d = 0.25, 95% CI: 0.08-0.42). These results are larger than the average effect sizes reported within professional development literature that apply coaching elements to mathematics programs.