English is hard, especially for native speakers
One of the hallmarks of the JET Program is that, hypothetically, as long as you've got a bachelor's degree in any field and are a native English speaker, you're eligible to apply and have a fair chance of being accepted. But over the course of my year here, it's become clearer and clearer that maybe that shouldn't be quite enough.
It's funny how lazy being a native speaker of a language makes you. Because you understand everything intuitively, you never question why things are the way they are or how exactly two similar things are different. The etymology and real meanings behind even common words fly completely over your head, and you're often left struggling to explain why a phrase can mean something so counterintuitive to its individual parts.
Being a language teacher with no formal training calls your attention to these gaps in knowledge even further, and while I consider myself pretty well-read with an above average grasp of the English language, I find myself in these sorts of situations far more often than I'd prefer to admit.
Earlier this year, a teacher I work with asked me to double check a powerpoint she was going to be using in class that day. The students were learning how to compare things, and one of the examples read something like, "Mt. Everest is higher than Mt. Fuji." Clearly, that's a little off. You'd want to use "taller" in this case. Yet, when talking about the summits of the mountains, "higher" is more appropriate. And maybe you got it right away, but it definitely took me a few minutes to figure it out well enough to explain to her why I was telling her to change her wording to something that sounded basically synonymous. ("Tall" refers to the height of something from bottom to top whereas "high" refers to the height of an individual point. E.g., you would say that a building is 20 stories tall while the ledge is 20 stories high)
More recently, I was caught in a slightly trickier situation, which I'm still not sure if I was able to explain properly or not. This time it was less about a difference in actual meaning, and more about a difference in nuance. The second years just covered "already" and "yet." And although these two are very distinct when used in statements ("already" for the positive and "yet" for the negative), when it comes to using them in questions, the line between them begins to blur. Thankfully, the text only introduced the students to the "already" form of the question ("Are you already at the station?"). But the teacher knew that "yet" could also be used and wanted to know if there was a difference ("Are you at the station yet?"). At first, I was inclined to reply that they really were interchangeable, but after saying each a few times, I realized that wasn't exactly the case. I ended up saying that "already" implies that you expect/hope for a negative reply, and "yet" implies that you expect/hope for a positive reply. For example, if you were running late, you'd call and ask, "Are you already at the station?" But if you've been waiting for a while, when you call, you'd ask, "Are you at the station yet?" However, there definitely are cases where they are more interchangeable ("Have you eaten yet?"/"Have you already eaten?")
The most difficult thing I've found, though, is trying to explain why we might not say something even if it is technically correct. In fact, I still haven't quite figured out how to explain these sorts of things very gracefully, so for now I usually just sit back and let them use it. Because, I mean, it isn't wrong. One of the most common examples of this that pops up in my classes is the word "enjoy." The students as well as the Japanese English teachers tend to use it a lot more liberally than I myself would. For example, where I might say "I went to see a concert this weekend," they might say "I enjoyed a concert this weekend." And though I do attribute this to a case of taking a Japanese word's meaning and context and translating them both directly into English, it's really hard to find enough fault with the usage to warrant pointing anything out.
On top of all this, a lot of these little linguistic points could also easily differ between dialects. Given that there's so many different types of English (even within the United States alone!), I don't doubt that there are people reading this who might disagree with how I've tried to explain things.
In conclusion, English is hard, and I praise the Lord daily that I'm a native speaker.