lessons The lessons are for schoolclasses of about 25 students, in which experiments are grouped around a theme, for instance 'air pressure'. The lessons consist of five phases: 1. introduction In a central conversation the students are introduced to the subject. For instance, questions like 'Is an empty bottle really empty?' are discussed. 2. activity After the introduction, students can do different experiments by themselves. The class is divided in groups of tree students and the different experiments are spread around the classsroom with their ingredients. Because there are more experiments htan groups, each group can work at their own pace. 3. ordering To stress the theme and order the different conclusions from the students found by doing the experiments, the students are asked to do a concluding assignment. This can be for instance a short essay on the theme of the lesson in which they have to use what they found in the experiments. These assignments are checked by the teacher for misconceptions. 4. conclusion In a concluding central conversation, the students review what was learned in this lesson. The teacher can ask questions like 'What can air pressure do?' 5. repeat exercise Finally, a repeat excercise is done several days or even weeks later. This is a spectactular experiment that the teacher performes in class and discusses with the students. In this way, the teacher can see to what extent the lesson is consolidated.