What do you think is the teacher's worst enemy? Some would say lack of time. Others would say unsupportive leadership, or the dreaded government inspection. Rigid curriculum, lack of resources and bad student behaviour may also be high on the list for many educators. For me, the worst enemy is bad theory. Bad theory, when accepted without challenge, can lead to bad practice. It's insidious, because bad theory that is accepted as fact without a full understanding of its implications, results in bad teaching, and ultimately, learners will suffer.