Don’t leave your manners on the doorstep
When you come inside, don't change your good behavior.
A person who has manners is respectful and polite.
Some people have manners when they are outside with strangers or friends. But when they come inside their own house, they are not polite or respectful towards their parents or brothers and sisters.
So mother asks them to be as nice and polite with their family members as they are with strangers, teachers and friends.
Mother also uses it when she takes her child to visit her friends. She says, "Don't leave your manners at the doorstep." She tells him to behave while they are visiting her friends.
