It’s why my kids are still “Language acquisition.”

They are 100% fluent conversationally (Germans recognize their Munich accents) but would have difficulty with things like literary analysis in German because they don’t have the cultural background like a native German with German parents. They do all read and write very well, though.

I would estimate that 60% of my students are fully bilingual. Another 20 % are at least trilingual (2 non-English native parents, plus education in English). G16’s best friend is native proficient in English, Turkish, and German, and proficient in Mandarin. I have another student that is Turkish, Hungarian, English, and German fluent. English-Spanish-German. The list goes on. My students amaze me every day. But the key to that is mother tongue development. Additional languages are easily acquired if mother tongue skills are good.