In high school, I had a German immigrant, fresh out of college as an instructor. The moment one stepped into that classroom to the moment one stepped out, nothing but German.
Hell, it didn't stop there. If you tried to talk to him at all, in or out of the classroom, he wouldn't acknowledge you unless you spoke to him in German, and he would only speak German to you.
Strangely enough, the German students were the only ones capable of holding conversation in a foreign language.
I graduated in 2008, haven't 'used' German in 7 years, but I still find myself thinking in German every once in a while.
Immersion (even for ~50min, 5 days a week) is easily the best way to learn. I don't know why anyone wastes their time with anything else.
EDIT: Hah, I just remembered how he never cared that we talked to each other during class about whatever, just that it was in German, not English.
I think once you're somewhat proficient in the language, this is true.
I'm currently taking Spanish courses in uni, and my professor is from Cuba. She's the sweetest lady, but has a tendency to ramble off in Spanish. About 50-60% of the time I can (vaguely) follow her, but the rest of the time I'm just hopelessly lost. And judging by the silence the rest of the class has a tendency for, I'm not alone.
Anyway, I'm certainly not trying to counteract your point, just to say that there are steps up to 100% immersion that I feel are necessary.
Immersion and osmosis are going to work a whole lot better if you're going from French to Spanish, or English to German, etc. There's enough shared vocabulary and culture that it's easier to make assumptions about the intent of the speaker.
That will not be the case if you're going from English to, say, Korean. Immersion is important for any language learning, but some prerequisite learning is needed to take advantage of it. I think those prerequisites stack up as you move further away from the foundation of your current languages.
I spent a year in Israel and wanted to learn the language (spoiler: I failed). The language courses (Ulpan) there started in Hebrew on day one. I knew not a single word. It was pointing at things, using your hands and .. a new language.
I liked the concept and I do like the language, even though I never made it.
During my time we started with English in 5th grade/at age 11 I think. And I'm still having trouble believing that these lessons were English only / full immersion right from the start, but .. I wouldn't know anymore, tbh.
Again, thanks for enlightening me.
In the US, yes. Or, at the very least, at my high school.
The other classes had weekly vocab quizes and grammar tests, with English instruction, whereas we learned German... in German.
Before the kids were born, I spent a while studying an Assimil course (a fine course, from a French publisher, for people who like to learn mostly through osmosis with some notes). Afterwards, I plowed my way through 450 pages of a French non-fiction book, understanding maybe 75%. So when my wife started speaking French to the kids, I could kinda-sorta follow.
Several years later, I decided to improve my French. I forced myself to speak it as much as possible, and I read another 10,000 pages (about 40 novels' worth). I also bought DVD box sets of easy series and watched them straight through. Happily, my brain decided, "Oh, so it's French or nothing. Better learn some French, then."
Today I watch French TV and read French novels without much trouble. I can converse with French preschoolers, but adult conversation is a bit tricker—my spoken vocabulary is more like that of a bookish 9-year-old than that of an educated adult. On a good day, this doesn't slow me down much. I could probably work as a programmer in French, but I'd have trouble negotiating a consulting deal without more immersion.
Ironically, I currently speak French better than my kids do, because I get more exposure. Given the right environment, the brain seems to adapt.