For each event there is a committee. The composition of this committee is diverse and consists of mathematics teachers and (assistant) professors (with special interest in mathematics education). See who are the committee members of the Mathematics A-lympiad, the Mathematics B-day and the MathDay15. [link to those pages]
The committees design the assignments, organize the events and judge the reports in the Netherlands.
These assignments are designed by the committee of these events. The committees make sure that the assignments have a low entry-level and a high ceiling, which makes the assignment accessible and challenging for every pupil.
In the assignment Inquiry-Based Learning is central. This means that pupils have an inquiring role and are even actively involved in the development of knowledge and skills. The pupils start every day with a number of introductory problems to get to know the subject. After these initial problems, they work on the final assignment. This assignment does not have a clear-cut answer and pupils are expected to choose their own strategy and use arguments to support their solution. To do this, pupils have to use creativity, planning skills, additional tools and teamwork.
To judge the reports, the committees pay attention to mathematical correctness, creativity, consistency of assumptions, cohesion of the story, and the underpinning of choices among other things.