When are children old enough

At what age do we start giving our children more responsibilities? What can they handle and when? My daughter just turned 7. I feel like she should be able to do more for herself. She is old enough to participate in her care. Simple things like putting shoes on the right feet (UGH), or on the mornings that she wakes up before me, starting her morning routine (brush teeth, go to the bathroom, etc), why do these activities have to wait until I am up and moving around?

I have been thinking.....

When will she be old enough to brush her teeth properly, pick out her own clothes for school, brush her hair, etc, pretty much get herself ready without me running behind like a drill sargeant trying to get her out of here on time. I am always telling her you are 7 years old, you are old enough to do this or that on your own, mommy will not always be here.......