This paper is based on research that investigated the development of probabilistic language and thinking by students 10-12 years old. The focus was on the adequate use of probabilistic terms in social practice. A series of tasks was developed for the investigation and completed by the students working in groups. The discussions were video recorded and complemented by the students' written notes. The analysis was carried out under a historical-cultural perspective. We have identified how some notions about frequency, chances, possibility and probability are intuitive and how others are mistaken. Subjectivist probabilistic thinking is present in students' ideas, and this indicates the need to develop teaching approaches that confront and overcome these ideas.