Time needed: as long as the topic needed, but the best duration is maximum 15 to 20 min, in lower levels shorter times and more students in one lesson is more effective 5 to max 10 min per students, in higher levels the teacher can play with longer teaching time, sometimes also partner preparation from one lesson is possible.
Why? The best absorbed knowledge will be made when students have to prepare a part of a lesson or the whole lesson by self. Beside of that this method is supporting an understanding for each other students-teachers side.
When? Before or after a new topic will be taught. Before the students will be responsible for the research by self, that’s most exciting for students to discover topics by self. After a taught topic the teacher and the students for self as well will have the control about absorbed knowledge.
How? The teacher will give one students to prepare a new topic or an taught topic to hold this alone in front of the class by self. In lower levels its more enjoyable if the lesson will be prepared in shorter durations with different students. In higher levels the teacher can also use the possibility to let two students in partner work to prepare the lesson.
Any risks? The students will teach mistakes, but there is an old sentence: We all are learning from our own mistakes as most.