matureとimmatureで西村先生のことを思い出す

It's immature of my junior high school teacher to have a bad mood in class because of his team losing a game the other day.

先日彼のチームが試合に負けたのでクラスで機嫌が悪いのは私の中学校の先生の未熟なことです。

because his team lost in a game the other day. (edited)

先日彼のチームが試合に負けたからです。