This paper reports on the analysis of the voluntary uptake and use of the "Nokia Mobile Mathematics" service by 3,957 Grade 10 learners. It measures the effect of the service on the school Mathematics attainment of 1,950 of these learners over one academic year. The study reveals that 21% of Grade 10 Mathematics learners voluntarily and regularly made use of this mobile learning resource outside of school time, with little involvement from their teachers. We found that across the group of 1,950 learners, there was an average decline in Mathematics attainment from Grade 9 to Grade 10 of 15 percentage points. We further found that there was a significant difference in the percentage point shifts of the group of non-users (zero questions), where there was a mean decline of 19 percentage points compared to the group of "regular/extensive users" (151+ questions), where the mean decline was 11.5 percentage points. This difference in means was significant (t (1344) = 8.0, p = 2.2 x 10[superscript -15]), with a small to medium effect size (d = 0.45). Research limitations and directions for future research are discussed in light of these findings.