Content, rhetoric and structure are the common areas for assessment of writing in Chinese by primary and secondary school teachers. This traditional assessment method is rather subjective and sometimes not reliable. There is also no rationale in the teaching of practical writing. In this study, the theories of communication are used to construct a marking scheme to assess the communicative abilities of school students. The new assessment method has been compared with the traditional method. It is found that the former is more effective. The findings are useful for assessment of writing and teaching of writing.