This was certainly true of my Polish ancestors. My great grandfather arrived at age 19. He never really became fluent in English but could get by when he needed

This was certainly true of my Polish ancestors. My great grandfather arrived at age 19. He never really became fluent in English but could get by when he needed to. My grandfather spoke both Polish and English but only spoke English at home once he had school aged children. My father really only knew the Polish swear words and I know a handful of Polish phrases that only get used amongst family at Thanksgiving or Christmas. Don’t ask me to write them down. I’ve only ever heard them verbally.