"I came here with good intentions. Something changes over time.Your belief that you are making a difference in the students’ lives turns into a lost cause. Your belief that they (students/teachers/admin) give a rat’s ass – disappears. Your belief that they are actually capable teachers – vanishes. You will remain, alone, to spend your year in purgatory. Teaching in South Korea is the midway point of nowhere. You won’t grow professionally or skillfully. You will instead grow to hate your job."
From Teaching English Sucks in Korea, I couldn't have said it better myself.