Analytical writing serves to learn and communicate learning. Our goal was to determine the impact of students' bilingual profile, defined by self-evaluated bilingual competence, use of language(s) for mental operations and language(s) use across different contexts, on their developing analytical writing abilities. Catalan/Spanish bilinguals -- in 6th and 10th grade and university students -- produced three texts on the same topic along a set of classroom activities, and a fourth one, on a different topic, one month later. We traced changes in text length and structure as indicators of proficiency across school levels and texts and tested the contribution of participants' linguistic profile on the observed changes. A Structural Equation Modeling on indicators of proficiency as growth parameters yielded a positive effect of self-evaluated bilingual proficiency on text length of the initial productions, whereas use of language for mental operations affected the rate of length increment across texts. Participants' self-evaluations of their linguistic proficiency did not affect text structure. The multidimensionality of bilingualism contributes differentially to proficiency in analytical writing.