It's good to each your child new things.
Mary has two kids, John and Jack, and John is older.
Mary wants the kids to clean the floor.
Mary asks Jack to watch and learn how John is cleaning the floor so that he can share the workload.
Mary does not ask Jack to try cleaning the floor because she thinks he is too young, but instead assigns the job to John every week.
John feels proud and shows Jack how he can do the cleaning better, and Jack happily agrees to help.
John feels unfair and refuses to do the cleaning job.