This paper is issued from the work of my PhD thesis (Lacek, 2023) analyzing the onditions and constraints of the implementation of inquiry-based mathematics education within the International Baccalaureate (IB). In the IB, towards the end of their secondary studies, each student must produce a written and individual piece of work entitled Mathematical Exploration (ME) that should involve an investigation in a field of mathematics. In this paper, I present a case study of a student’s work on a modelling ME, show the effect of the teacher’s regulations on the evolution of the milieu and point out the complexity of organizing an appropriate experimental milieu for a student at upper secondary level.