1. Respect children's privacy: children's rooms are their private spaces, and there may be some things or information that they don't want to be disturbed. Knocking on the door is a way to show respect. Tell your children that you are here and respect their private space.

2. Avoid sudden entry to scare children: children may do some important things in the room, such as doing homework and playing games. Sudden entry may interrupt their thinking and bring them pressure. Knocking on the door can prevent this from happening.

3. Cultivate children's sense of politeness: knocking at the door is the basic etiquette. Through this behavior, children can be educated to respect the space and time of others and cultivate their sense of politeness.

4. Remind children to pay attention to safety: Sometimes, children may forget to close the door or leave it unlocked, which may pose a threat to their safety. Knocking on the door is also a way to remind children of safety.