PURPOSES: to analyze the proficiency in written expression, classifying the errors of orthographic production, which occurs during the first four grades of elementary school, identifying the most frequent and monitoring their developments, comparing the performance by grade and by gender. METHOD: a cross-sectional study was conducted in the population of students from 1st to 4th grade, in the city of Porto Alegre. 214 subjects were assessed by the standardized saying of the School Performance Test. RESULTS: we found higher sufficiency levels in the field of writing for the initial series. On the 4th grade the level of performance was considered to be lower with grammar emphasis' rules. Analyzing the test, it was evidenced that the errors of multiple representations, were the most frequent in this population. When the different types of orthographic errors of the four grades were analyzed together, we observed that there was a significant difference between them (P<0.05), except for the errors of joining and separating (P=0.09), confusion in the endings am x ão (P=0.36), oral/silent exchanges and confusion with letters alike (P=0.27). There were more orthographic errors and less written expression domain for male gender, but it was not statistically significant. CONCLUSION: analysis results show that orthographic errors had a moderate reduction for students in the 4th grade, however, the same did not occur with the level of sufficiency in the domain of the written expression that involves complex contextual rules.