Due to corona virus, school has been called off in Japan and most of the students cannot go study in their schools. As one of the measures that students can study under this situation, online video lesson has begun to be prepared and uploaded by school and education committee in each local area. Before this disaster, the number and contents of such online lessons were very few and less used in Japan. This is obvious even compared with other developed countries. I think this is good chance to make and to distribute the video that has all contents of curriculum of the lesson based on the school text book, and it should be continuously used for making the best of the videos by all student even after finishing this school class closing term. These are three advantages to keep preparing the video lesson even under ordinary terms. First, a student who is absent from a class because of sickness such as flu can have chance to learn the content of the lesson by using the video at home after recovering it. Secondly, a student who cannot go to school due to any reasons can also have chance to learn every topic of compulsory education curriculum at out of school via the video lesson. Thirdly, to use it for reviewing a lesson already done. If a student did not understand a lesson in class or forgot it, he/she uses the video lesson for review later on by themselves. If the student cannot understand the content only once, he/she can watch any time repeatedly. Especially, during long term off like summer holiday has lots of time, so the video can be useful to review the lessons that students has already learned in the previous term. As just described these merits above, it is very beneficial for many students to be prepared such official video lesson by school and government.