In the subjects mathematics, physics and chemistry it is noticeable that students have great difficulty with the metric system. An analysis of test results, observations and interviews shows that the metric system is an arithmetic/mathematical component that many students experience as very difficult. In an attempt to understand this problem, research was conducted in the form of a Lesson Study, this is a method in which teachers work in teams to go through a cycle to make the learning of students transparent. The starting point for this Lesson Study was the vision that a good understanding of the metric system is closely related to a good understanding of the decimal system. A lesson was therefore designed in which the link between these two concepts is central. This lesson was conducted at two secondary schools in Friesland in the first two years with mavo, havo and vwo level. The following design features were used in this lesson: self-discovery, guiding questions, Van Groenestijn action model, practice, differentiation and collaborative learning. By observing, interviewing, analyzing and exchanging thoughts of three types of students (strong, average, weak) an answer has been given to the question: ‘how do students learn when the connection is made between the number system and the metric system’. The chosen analysis shows that there is a large group of students who make the connection after our intervention. The different design characteristics contribute to this to a greater or lesser extent. Going through the action model of Van Groenestijn seems to contribute most to making the connection between the decimal system and the metric system.
Our research has been applied to one research lesson. In an in-depth follow-up study, a larger series of lessons over a longer period can be examined. In this case, it can be chosen to apply this methodology at different schools of different levels and across school years and subjects.