NO!! In fact, most schools request that the teacher ONLY SPEAK ENGLISH in the classroom. This encourages the students to start thinking and talking in English.
You can get by living in Korea without ever learning to speak any Korean. There will always be someone willing to help, and people are quite patient and often more than happy to practice their English skills with you.
Many Churches, universities and Cultural Centers offer free Korean classes to foreigners. Many foreigners learn Korean and find it enriches their experience. Korean people are always very impressed when foreigners talk to them in Korean. It shows that you respect the country and the culture.
