This contribution presents a new type of reflective writing assignment introduced last year (2014-15) for 2nd-year Master’s students doing their degree in secondary education and student teaching at the School of Education (ESPÉ) of the Université Paris-East Créteil (UPEC). The writing assignment is based on the analysis of observed lessons the students conducted in their schools. By providing precise guidelines for procedures and the written document itself, the assignment aimed to foster students’ ability as novice teachers to adopt a reflective stance with regard to their teaching practice and to help transform first-hand classroom experience into professional knowledge. The survey was carried out on a corpus of 30 texts collected from students teaching two disciplines (e.g., French and History) in a vocational high school. The data, exploited using a sociolinguistic approach, including various discourse analysis categories, revealed a typology of four distinct models of text production. The results show differentiated reflective processes both in terms of nature and expression, suggesting that students’ professionalism developed in a diverse variety of ways. Questions remain concerning the efficiency of the tool, how to improve it, how to define a more rigorous use of it by both student and tutor, and what measures may be taken for a more integrated approach to the development of reflective skills.