Objective: The present study was conducted to analyze and compare the written discourse of EMR students according to experiential metafuntion introduced in Halliday’s systemic functional grammar. Method: The present research follows a descriptive method. The informants (311 students) were chosen among the primary, prevocational guidance school, and vocational high school students in 2009. The informants were chosen according to multi stratified cluster sampling. A written test in the form of picture stories was administered to 311 students. Results: At first, the data (consisted of 2407 clauses and 10861 words) was analyzed concerning the type of process (verbs) used in clauses. Material (58%) is the most frequent process in all grades. Behavioral, relational and verbal clauses happened in 13%, 12%, and 10% of the clauses. Existential process is the least frequent one (0.1%). Conclusion: Nonparametric statistical test (x² test) shows that even when p≤0/001, x² value rejects the null hypothesis. In other words the two variables in the research (different grades of EMR students and their use of different processes) are not independent; hence the grades of EMR students and their use of different processes in their writings are related. The frequency of different processes varies in different grades. Also the frequency of material process decreases as the grade increases, and frequency of mental processes increases as the grade increases. EMR primary school students mostly use relational and material processes in their written discourse. EMR guidance and high school students use material, behavioral and mental and verbal processes more than the primary school students. It seems that the findings are compatible with Piaget's cognitive development and accredit it.