I’m struck by the uniformity described. I've known people with a knack for languages, and in the US system they can opt to take more courses or go further. What do exceptional English-learning students do?
It's also worth noting that most public schools have (short) study abroad programs that will allow excellent students to apply for a few weeks in Australia or New Zealand as well.
One other interesting part of the uniformity is that perhaps because of the English focus, there's no real exposure to other foreign languages in public schools before the high school level (and sometimes not even then). Whereas in the US, I think most people have the option to study something from middle school or junior high.
I'm excluding Mandarin from this discussion, which is sometimes touched on superficially in Classical Japanese.
In hindsight, I'd say the most important for learning English was that I was an ignorant teenager. I just... typed completely broken sentences into forums that today I wouldn't even be able to fathom how could I get the grammar so wrong. I got banned several times from Freenode channels, for pestering people with unintelligible questions and then not being able to understand the answers.
I was unaware and shameless and that shamelessness allowed me to make progress. Were I to learn English today, I'd probably be too self-aware to embarrass myself trying to use a language I can't use, and that would make it far more difficult to learn anything.
I suppose that's a good life lesson in general. You can't get good at something without being embarrassingly bad at it at first. If there was a pill to make you unaware of your own embarrassing self, that would be a learning pill. In fact, I guess we should really be learning new things while drunk!
Not to toot my own horn, but I moved solely on my own accord. Sure, I have a work visa, but that was for convenience, not necessity, whereas many immigrants come for a short term job that turns into something more or because they are fleeing from war or disaster. I entered with the mindset that I need to learn the language and putting it off is just hurting my future self.
When people ask me how I learned so fast, I told them the truth. I don’t have much else to do in my free time so I “study”. These days, I even browse Reddit in my target language. I believe people are really quite capable of learning language, especially adults! But it requires intentionality and practice be develop proficiency, like anything really. If you want to get good at languages, you have to speak, read, and write every day.
To bring it back around, many of the best English speakers I have met engage parts of their life in English that they don’t need. Leisure and entertainment are the top contributors but depending on your profession, it could be required to speak/read English at work as well. It goes to your point of how the excellent students learn and I think everyone can apply to these ideas to learning across a wide range of topics.