Is it better for a nine-year-old boy to practice Taekwondo or calligraphy?

These two things do not conflict!

Practice Taekwondo to strengthen the body, exercise the body and mind, hone the spirit of struggle, standardize etiquette and classroom discipline.

It is also a good thing to learn calligraphy, cultivate one's morality and cultivate one's character, and write good handwriting from an early age. As long as the time periods do not conflict, both can be done at the same time.