The present study explored the writing development of 134 second-year high school students of English as a foreign language(EFL) in Spain over one academic year. In order to assess students’ writing performance from a communicative perspective (Usó-Juan and Martínez-Flor, 2006), their essays were examined by means of an analytic rubric especially designed for this investigation in terms of these dimensions: content, task requirement, coherence and cohesion, grammar and vocabulary. In addition, we sought to examine whether proficiency level had an impact on the dimensions in the rubric. The results show that the most proficient students performed better than the rest of participants along the school year. Moreover, positive correlations were found between learners’ writing achievement and their level of proficiency in all the dimensions explored thus suggesting that advanced learners outperform their lower-level counterparts. In addition, the analytic rubric proved to be a useful tool in the assessment of students’ performance.