Dumb Girls In Puberty!!!

Based on the CG set/voiced game by Maron☆Maron (まろん☆まろん).

The protagonist is a teacher in a small garden. One day girls in the garden who ate cookies that induce a rapid physical development become grown-up. They behave just as their usual days despite the voluptuous bodies... Receiving lots of their unintentional temptations, his patience is about to run out...

(Source: DLsite English)