ni hao. wo you yi ge hai zi. ta jiao jang xue jia. ta jiu sui le.

hi. i have a son.he is 9 years old.we would both like to learn mandarin preferably for high school exam.

ni hao. wo you yi ge haizi. ta jiao jang xue jia. ta jiu siu(sui).

你好， 我 有 一个 孩子，他/她叫  jiao jang xue jia。他/她九岁。

hi. i have a son.he is 9 years old.we would both like to learn mandarin preferably for high school exam.

Welcome to the world of Chinese culture~~:)

ni hao. wo you yi ge haizi. ta jiao jang jiang（I feel that what you want to say is Jiang)xue jia. ta jiu siu sui.

hi. i have a son.he is 9 years old.we would both like to learn mandarin preferably for high school exam.

你好，我有一个孩子，他叫jang xue jia。他九岁。