Many people mistakenly believe that in order to teach languages it is enough to be a native speaker. Well, who cares what some sad ignoramuses think, you might object. Sadly, said ignoramuses can be found among university faculty more and more often. There are colleges that have disbanded their foreign language departments and have given the teaching of languages to the native-speakers among students. Needless to say, this system of language teaching cannot possibly work.
I have been teaching languages for more years than I care to mention. If I do, people might think I'm on the verge of retirement, which is completely untrue. I think that I kick ass at language teaching, and my students seem to agree unanimously. The only language among those I speak that I cannot teach, however, is my own. I am a native speaker of Russian, which is the language that I speak at home. I attempted not even to teach it, but to tutor somebody in it a while ago. It was a complete and total failure. I couldn't answer a single question my students asked me. "So why do you conjugate this verb like this?" they would ask. Or, "How many verb groups are there?" And even though I have been speaking this language my entire life, I had no idea what to tell them. I didn't know which grammar points would turn out to be especially hard to the students and how to make them clearer. I had no idea why I was speaking the way I was and couldn't explain it to the students.
Teaching languages is a skill that it takes people a long time to acquire. Being a native speaker of the language is completely irrelevant to whether you will be able to teach it. In their push to eradicate the Humanities, university administrators try to substitute tenure-track teaching faculty with underpaid, overworked, and often woefully underqualified part-time instructors. This measure seemingly saves money for colleges. Tenure-track and tenured faculty teach a limited number of hours, expect to have sabbaticals and course release time, and cannot be forced to teach 9 courses per semester with no TA.
This measure always turns out to be counterproductive. As a tenure-track faculty who only works two or three days a week, I have the leisure and the motivation to design complex, engaging, and original learning activities for my students. I have the knowledge necessary to ensure that every aspect of the activity has a pedagogic rationale. I am invested into making sure that the students do well, since in all probability I will see those same students in my higher-level classes and I want them to be prepared for that. I have time and energy to get to know all of my language students personally and help each of them overcome their personal struggles with the subject matter.
Aside from being a lame attempt at saving money, squeezing foreign language and literature courses off the campus has an important ideological goal. Our classrooms are always small and are organized around students talking, expressing themselves, and doing all kinds of creative things during the entire class. This is not a huge lecture in macroeconomics, where hundreds of students are sitting in complete silence for 2 hours, being indoctrinated by the professor and never getting a chance of formulating their own opinion, let alone expressing it.
At the same time, speaking another language requires adopting different ways of thinking, seeing the world, relating to your reality. It is a lot more difficult to zombify a person who has developed alternative modes of relating to the world. This is precisely why so many efforts are being made to prevent American students from learning about other languages and cultures.