Grandfather rule

The grandfather rule is like a special kind of rule that sometimes exists when something new happens or changes. Imagine you have a favorite toy that you always play with, but then your mom or dad buys you a new toy that's even cooler and you want to play with it instead. But your mom or dad says, "No, you have to keep playing with your old toy because of the grandfather rule."

It’s the same thing with some rules. Sometimes, when there's a new rule made, people who already followed a different rule before the new one was made can keep doing things the old way because of the grandfather rule. It’s like the old rule is still allowed to exist for those people, even if it’s not allowed for others.

Let's say there's a new law that says everyone has to wear helmets while riding bikes. But some people who have been riding bikes for a long time, before the new law was made, are already used to not wearing helmets, and it feels weird for them to wear one now. So, because of the grandfather rule, they are allowed to keep riding without a helmet, even though everyone else has to wear one.

It's important to have the grandfather rule so that people who are already doing something one way don't suddenly have to change everything they're used to, all at once.