What do the brackets 1 and 2 mean in the recruitment of teachers in Haining Primary School?

The primary school stage is divided into three parts: the first part (1-2) is the critical period for students to form habits, at which time students have strong imitation ability and lack self-control and judgment of right and wrong. In the second part (3-4), students' basic habits have been formed and their courage has gradually begun to grow. This is the time when they began a hazy period of restlessness. If teachers don't guide strict management in time, their later work will be a bit difficult once their little actions form a small "victory". The third part (5-6) Children's habits have basically developed into nature, although children at this time are a little budding in adolescence. If teachers are well educated and parents cooperate effectively, these students will be excellent. Therefore, children in primary school are a critical period for habit formation.