I'll Be My Own Teacher
Nobita's parents decide to get him a tutor as his grades are bad so Nobita decides to use himself 3 years in the future to answer his school questions now. But his future self is dumb because Nobita did not study and that Nobita too has a future self who turns up and complains that he is dumb too because Nobita 3 years in the future did not study either. The three of them go to the kindergarten Nobita, saying that if they want to improve their grades,they have to start from the beginning. However none of them has the heart to tell the kindergarten Nobita to study, so they return to the present time.
Aired 23/05/1979EP 45 - I'll Be My Own Teacher
Doraemon
Nobi Nobita is a 4th-grade boy in Tokyo. One day, a round, blue cat-style robot (minus ears) pops up in his desk drawer. Nobita's great-great-grandson (or something) lives in the 22nd Century, but thanks to Nobita's mistakes, the entire family is living in poverty. To rectify this, Nobita's descendent is sent Doraemon back to the past, to help prevent Nobita from making mistakes. Of course this is a difficult task since Nobita is the weakest and least intelligent child in his class. Doraemon does, however, have a 4-dimensional pocket on his front, which contains cool gadgets from the future. With these toys, Doraemon will try to help Nobita. Unfortunately, Nobita also has the bad habit of misusing Doraemon's gadgets and landing himself in yet more trouble?
(Source: AnimeNfo)