In this article we present the results of a qualitative research study on the pedagogical factors that influence English teaching in four public schools of Medellín, Colombia. Twelve teachers were interviewed regarding three linguistic principles: communicative competence, native language effect, and interlanguage. The data analysis led to the identification of various factors, such as teachers' linguistic ego, view of their teaching role, and attitude towards English, which shape English teaching and are tied to teachers' education. It was concluded that teachers' professional development must tap into these factors so teachers can effectively revise their beliefs and adjust their practices to ensure a high quality in their teaching.