4 - 6 years old
Your child's independence will grow almost exponentially during these years. They'll go from trying to do things on their own, to really being able to do most things for themselves such as: picking clothes and wearing them, cutting up their own food, going out to play with other children independently.
During these years you should encourage children to engage in safe "rough and tumble" play with one another. This will encourage healthy competition, and will strengthen their muscles and bones against the perils of the world.
By six years old they'll be able to play organized games with other children their own age, such as football, soccer, rugby, or baseball. They'll understand the rules together, and also that breaking these rules will result in other children not wanting to play with them anymore. This socialisation prepares them for growing up in the real world.