I'm from a small Dutch bordertown and my first language is a dialect that is part German, part Dutch (and some French) (Limburgish). In German class, away from

I'm from a small Dutch bordertown and my first language is a dialect that is part German, part Dutch (and some French) (Limburgish). In German class, away from that bordertown, outside where the dialect is common, I never paid attentention. Teachers would require me te learn tables filled with exceptions, weird strings of words (mit nach bei..) etc. I simply refused. I often didn't bother to go to class. Just using the Fingerspitzengefühl that comes with the part-German dialect, was adequate. 7/10 on my exams. So certainly not fluent or even good. At the diploma-handout, the German teacher told me she did not want to, but was required to give me that grade (why a teacher would disclose this to an 18/yo is beyond me, though. There certainly was spite). Point is: even sideloading a language from a young age helps learn it. At least for n=1.