Natsu jikan no otonatachi

Takashi and four of his classmates, fourth-grade students, cannot succeed in doing a back pullover around a horizontal bar. Their gym teacher warns them: they have one week to succeed; if they resign now, then, tomorrow, facing life difficulties, they will always run away and become bums. Furthermore, all five must succeed, if one of them cannot do it, then all of them fail. Takashi is really worried and wonders if he won't be always the looser who couldn't succeed in the back pullover bar exercise. - IMDb