Create learning material

If you have gone to school and you know better about a subject, and it is your favorite subject, why. not start researching on it and specialize in writing about it.

This can form very good learning material for other people. Though you need to look at copyright laws that govern the use of any written and published material.

Later you can think 0f publishing and selling your own books. This is how writers become writers and earn a living through writing.