I agree with what you said about students not getting enough practice speaking in younger grades. Though I think it extends further than that. Even in High School they don't really get much chance to practice spoken English. A lot of the times the teachers are poor at speaking English too so they might make the same mistakes that should be corrected. Furthermore, the idea of losing face or being embarrassed is so integral to Chinese culture that it is counter productive when learning a language. In order to learn a language, you really need to make mistakes and be OK with it. Here mistakes are frowned upon. Well more than frowned upon. They are nearly unacceptable. All of this combined with the fact that spoken English isn't required on the Gao Kao or their exams, they don't really get a good grasp on spoken English.