Jijii is the homeroom teacher of class 1-D. He always has an armband on his left arm that has different text every time it's shown, the text being anything from the title of the episode to an adage. He is surprisingly lively for his old age and is seen as strange by his students, but the feeling is actually mutual. &quot;Jijii&quot; (爺, &quot;Jijii&quot;?) is used to address a grandfather or an old man in Japanese. He is known for using different &quot;scare tactics&quot; in order to keep his class in order, the first of which was his promise to stand by his students' beds if they were to skip class.    -wikipedia

The 11 year old Miyamoto Rebecca becomes the new teacher of a classroom which is full of weirdos. Despite her cute looks she's a little beast and can be pretty sarcastic and offensive. The school is not safe anymore now that she's in charge of a class and her students, Himeko, Ichijou, Rei and a white rabbit who took a liking to Rebecca help her to rough up the school and the neighbour-class with its teacher "ojii-chan".
 
(Source: Anime News Network)

Rebecca Miyamoto is a child genius with a Ph.D. from Columbia University, and she is starting as a high school teacher. The students love to tease her from day one, and she doesn't behave much better. Now we follow this class as they strive to get better grades and cope with their new teacher. 
Chapter count includes 22 bonus chapters