In case not enough caution is exercised in the assessment of second or foreign language learners’ writing performance, one cannot trust the accuracy of decisions made accordingly. As experts or trained raters are often not available or it is not cost-effective to employ them in most educational contexts, writing assessment is often carried out by language instructors, who may not enjoy an adequate competence in teaching and assessing L2 writing. This makes the investigation of the accuracy of ratings done by language teachers a must. In so doing, 30 language teachers in three groups, each with a different background in teaching English and L2 writing, were selected, and their ratings of 30 IELTS samples were compared against those of expert raters using One-Way ANOVA tests. A statistically significant difference was found among the raters for the total writing score as well as the four components, with the L2 writing teachers demonstrating the closest performance to that of the expert rater and with language teachers with no or very little background in teaching L2 writing demonstrating the lowest accuracy. Moreover, the only significant correlations were found between the ratings done by the writing teachers and those of the expert rater, indicating that only they could interpret the scoring criteria not significantly different from the expert rater. The results demonstrate that language teachers are not generally suitable writing raters as they are affected by their own teaching background and understanding of the rating criteria.
