This is the 10386th most frequent Japanese word.
黙る
To become silent; to say nothing.
Here, '黙る' is used to indicate the act of staying quiet or refraining from speaking, as is expected behavior in a classroom setting.
教室で先生が話している間、全員が黙るべきです。
In the classroom, everyone should remain silent while the teacher is speaking.
In this sentence, '黙る' implies a voluntary decision to not speak because of emotional reasons.
彼に怒っているので、しばらく黙ることにした。
I decided to stay silent for a while because I am angry with him.
'黙る' in this context suggests maintaining silence as a way to stay composed and not make the situation worse.