The video that is going to be analyzed in the paper was recorded at a language school in Melbourne. It demonstrates an adult ESL class studying English at a pre-intermediate level. The major challenge for the teacher consists in the fact that all the students have different cultural backgrounds, which implies that none of them share the same mother tongue. The class is comprised of students coming from Korea, Peru, Brazil, and Italy. The teacher, Monique, who is British, has been teaching these students for about five months. The major language focus of the class is the oral practice of Past Continuous and Past Simple tenses in their application to real-life situations. The students are asked to tell a story about a special occasion from their experience. The task starts with a brainstorming activity for students to recollect vocabulary on the topic establishing connections and associations that constitute one semantic field. Since all the students come from different countries, their cultural and stylistic traditions, as well as structural contrasts of their mother tongues, account for the fact that they conceptualize language differently. Theoretically, this implies that:  1. the students are supposed to segment the input coming from the teacher using different criteria and, therefore, understand the task differently;  2. they may select different language units when verbalizing a similar idea;  3. they use different links to connect events in discourse (Ortega 2014). Practically, these implications are taken into consideration by the teacher who creates an interactive environment encouraging students to assist and check each other. Besides the evident purpose of collaborative grammar and vocabulary acquisition, this is also done to share the students’ peculiar models of language conceptualization that reflect their worldviews. The paper at hand is aimed to investigate the major theories of second language acquisition in their application to the given lesson. It is going to analyze the way the language is taught and perceived by the students, the strategies applied by the teacher, the learning activities the students perform, and the feedback that they provide. The content and the structure of the lesson have been briefly summed up in the introductory part; the main body of the essay will be devoted to the analysis of SLA theories and aspects of the classroom language and activities exemplifying them; the conclusion will draw together the central points of the analysis and attempt to provide future directions for linking theory and practice. Key Theories of SLA and their Reflection in the Lesson There exist at least forty theories of second language acquisition; however, none of them manages to explain its nature exhaustively and completely. The task is complicated by the fact that the process of language learning is not linear and cannot be reduced to a set of simplified mechanisms as most theories attempt to do (Ortega 2014). Thus, it would be logical to assume that the real practice of SLA may unite features of several models as it can be demonstrated using the materials of the given lesson. Behaviorism Behaviorism understands SLA as a stimulus-response mechanism, which consists of acquiring positive automatic learning habits. The major emphasi