Deaf learners who use sign language have difficulties in learning foreign languages because they do not have a good grounding in the official language of their country, both in vocabulary and in comprehension and production. This means that although their understanding of the foreign language improves when it is combined with the official language in class, it is not fully effective. The lack of sign language training for teachers is also a factor, which makes it difficult for them to interact with their students. For students who are deaf or hard of hearing (D/HH), it is essential to supplement spoken language with sign language in order to better understand the lessons. If they are profoundly deaf, teachers focus on reading and writing in the foreign language, avoiding listening, whereas if they have hearing difficulties but communicate orally, teachers try to develop their receptive and expressive skills.

On the other hand, the difficulty of lip-reading in English or German affects the decoding of the phonemes of the words pronounced by the teachers, as well as the possible production of words by the (D/HH).

To improve this situation, teachers use visual aids to facilitate understanding of the foreign language. It is also recommended that (D/HH) sit in the front rows. This will help them to see the teacher or interpreter, the blackboard and to lip-read better.