Hello, the most famous English language training organization is said to be the New Oritenal. They have courses for students from little kids to adults. Some of my friends have participate in a series of English courses there before they go abroad. About three years ago, they have started a course called 'POP English' specially for kids.
One more is the Xi'an Hi-tech International School which enjoys high fame in Xi'an. It has courses from kindergarten to senior high school. I think you are qualified to apply for a position there.