It is known now that gambling among youth is a major problem around the world. Children and teenagers gamble and some of them become addicted to gambling. In order to help them develop mathematical knowledge about these activities without asking them to gamble, lesson plans about probability were designed and implemented in a grade four classroom. In this teaching experiment, students were asked to simulate the spinning of the wheel using a spinner. The analysis of the students’ representations showed that they used deterministic reasoning to predict the outcome. The awareness of variability of outcome occurred with the comparison of the frequency of each outcome, which helped them change their reasoning to a probabilistic one. Results also suggested that student conceptions about the fairness of the spinner could be considered as a form of critical thinking about the validity of the simulation.