Gakkou gurashi! manga

Gakkou Gurashi! summary:

Takeya Yuki is in love with the school. For her, it's a wonderful place, where she enjoys her school activities, especially the activities of her club: School Life Club. The club has Rii-chan as the president, Kurumi-chan as another member, and the teacher, Megu-nee, always there for them. Yes, she is in love with her school... on her mind. Because, for her, the reality of the school and their club's activities is way too hard to be perceived... From Batoto: Three high school girls and a teacher are camping at school. The First Article of the "School Life Club" Code reads: The School Life Club encourages a spirit of self-governing independence by camping at school, as well as socializing with various after-school clubs, which you can't enjoy from regular classes alone."