The revision process is in fact a process of structuring and shaping language (Fitzgerald, 1987; Somer, 1980; Stallard, 1974). Barr’s (1983) research has demonstrated that revision can enhance students’ writing ability. In the present study, “symbol marking” was tested on Form Three students from three local average-ability (Band 3) secondary schools. One Form Three classes in each school were invited to participate in the experiment. Students were asked to revise their own compositions two times. The first time, the compositions were marked first by the teacher using “tradition marking,” and students were asked to revise them according to the teacher’s markings two weeks later. The second time, the compositions were also marked first by the teacher, but using “symbol marking.” Students were also asked to revise their compositions two weeks later, according to the teacher’s markings. T-test results showed that “symbol marking” is a more effective way of marking students’ compositions. Students achieved significantly higher scores in the second revision where the teacher used “symbol marking” to mark the compositions. “Symbol marking” enhances students’ thinking and analytical ability because students were required to think and analyse each correction marked. “Symbol marking” can develop students’ sense of responsibility in their writing, and can facilitate students to become effective proof-readers.