静かだ
The children are quiet.
子どもたちは静かです
The children are quiet in the classroom.
子どもたちは教室で静かです
The children are quiet in the classroom during the lesson.
子どもたちは授業の時間に教室で静かです
The children are quiet in the classroom with the teacher during the lesson.
子どもたちは授業の時間に先生と教室で静かです
The children are quiet in the classroom with the teacher during the lesson because there is an exam.
子どもたちは試験があるので授業の時間に先生と教室で静かです