Gu-Pan!

From Overload Scans:

Washizu Miri, a second year high school student, is a small 148cm(less than 5 feet)-tall girl who has acquired a reputation for being violent and dangerous. This collection of short manga (generally 2 per page) chronicles the fun daily life of Miri and her friends at school, Natsumi and Utako.

Wikipedia The Doujinshi & Manga Lexicon Vol. 1 Vol. 2 Vol. 3