This study explored the role of student characteristics in studying micro teaching-learning environments. The overarching hypothesis is that teachers teach differently to micro environments in their classrooms. This study is the first of a series exploring the following four questions: (1) What student profiles are identified at the beginning of a school year with respect to cognitive and motivational-affective factors? (2) How do students with different profiles perceive conditions in their learning environment? (3) To what degree do classrooms differ in the composition of student profiles? (4) What are possible consequences for examining micro teaching-learning environments? The study investigated 82 randomly selected high school science classrooms. Student characteristics were assessed at the beginning of the school year. After a video taped teaching unit, students were asked to rate the degree to which they experienced learning conditions as supportive. Latent class analysis (LCA) showed five distinct student profiles that varied along cognitive and motivational-affective dimensions. Multilevel analyses showed effects of student profiles assessed at the beginning of the school year on the students' perception of learning conditions in a teaching unit 4 months later. To illustrate consequences for examining micro teaching-learning environments, student profiles were linked to video examples. The examples point to the special value of LCA in studying micro teaching-learning environments: they make it possible to focus on the individual student and to investigate the interplay of student characteristics and the learning environment.