Mitsudomoe Zouryouchuu!

Synopsis

Satoshi Yabe has grown accustomed to being class 6-3's homeroom teacher. Since his assignment, the Marui triplets have used countless antics to play around with him. As a result, however, Yabe and the sisters learn more about each other. Continuing their last year in elementary school alongside Yabe, the triplets and their classmates never fail to stir up trouble and play pranks on one another.

(Source: MAL Rewrite)