Leo (Adam Sandler) is a jaded 74-year-old lizard who has been cooped up in the same Florida classroom for decades with his terrarium companion, a tortoise (Bill Burr). When he finds out that he only has one year to live, he plans to escape to experience what life is like outside of that classroom. But instead he finds himself caught up in the troubles of his eager senior students in his senior year of elementary school, including an incredibly mean substitute teacher. Leo will end up taking on the weirdest yet most surprisingly comforting to-do list.