This paper refers to the effectiveness of an instructional sequence of lessons related to Probability, which were implemented to 11 to 13 years old talented children. This instructional sequence as part of a one semester math course, aims to develop children’s understanding of probability. Contextualized situations involve decision making into uncertainty, confrontation of intuition with experimental probability, and adhesion to theoretical probability. The pretest included equiprobable and non-equiprobable, independence and dependence concepts. Lessons were focused on students´ work, especially in pairs and small groups. Experimental situations always included plenary discussion, where the teacher acted as moderator. The posttest gave evidence of overcoming preconceptions and adhesion to the principles of theoretical probability.