According to the following text, what is the primary role of teachers in ESP courses?

While ESP teachers may have some understanding of the fields in which their students work, these teachers do not have to be knowledgeable in all of these fields. A degree in law or medicine is not required of teachers in ESP courses for lawyers or doctors. In ESP, teachers’ and students’ roles are different but complementary. Teachers are the language education specialists; they know (about) English in addition to having pedagogical skills. Students, on the other hand, have some knowledge of their professional field (generally in their first language) and usually have a real motivation to learn the language (e.g., communicate with clients, read a manual, be promoted). It is not possible to generalize, however, whether they know English.

SARMENTO, S.; VIANA, V.; BOCORNY, Ana E. English for Specific Purposes (ESP). TESOL Press: 2018.