The primary aim of this study is to gain insight into the level of formality in EFL (English as a Foreign Language) classrooms in upper secondary schools and in SFI (Swedish for Immigrants) classrooms in Sweden. This research specifically examines how EFL and SFI teachers perceive and integrate formal language into their teaching practices. Semi-structured interviews were conducted with 10 teachers, including 5 EFL and 5 SFI teachers to gather qualitative data. The interviews ranged from 20-45 minutes and were recorded, transcribed, and analyzed using a thematic analysis to identify recurring themes and patterns within the interview transcripts. The findings reveal distinct perceptions and practices between EFL and SFI teachers regarding formal language. EFL teachers view formal language as essential for promoting social norms, such as politeness and respect. They incorporate formal language using formal texts, advanced formal vocabulary, and sentence structures. Some EFL teachers prioritize the use of formal language based on specific lesson goals, while others are influenced by the informal nature of Swedish culture and prefer to use informal language in their classrooms. On the other hand, SFI teachers perceive formal language as flexible and context dependent. They emphasize practical applications of formal language such as writing emails and formal letters at a basic level. SFI teachers focus on clarity and correctness over strict formal language rules and the aim of such focus is to ensure that the students learn the basic Swedish language necessary for social integration.