Research on impact in student achievement of online homework systems compared to traditional methods is ambivalent. Methodological issues in the study design, besides of technological diversity, can account for this uncertainty. Hypothesis: This study aims to estimate the effect size of homework practice with exercises automatically provided by the 'e-status' platform, in students from five Engineering programs. Instead of comparing students using the platform with others not using it, we distributed the subject topics into two blocks, and created nine probability problems for each block. After that, the students were randomly assigned to one block and could solve the related exercises through e-status. Teachers and evaluators were masked to the assignation. Five weeks after the assignment, all students answered a written test with questions regarding all topics. The study outcome was the difference between both blocks' scores obtained from the test. The two groups comprised 163 and 166 students. Of these, 103 and 107 respectively attended the test, while the remainder were imputed with 0. Those assigned to the first block obtained an average outcome of -1.85, while the average in the second block was -3.29 (95% confidence interval of difference, -2.46 to -0.43). During the period in which they had access to the platform before the test, the average total time spent solving problems was less than three hours. Our findings provide evidence that a small amount of active online work can positively impact on student performance.