All of the evidence is to the contrary. The first generation raised in America overwhelmingly learns English—one study has found that 94% of immigrants raised in concentrated communities like South Florida and Southern California speak English “well” or “very well” by 8th grade (roughly age 13). As the charts I posted last year demonstrate, the language Latino children growing up in America don’t speak so well is Spanish. English abilities quickly improve through the generations; Spanish skills quickly decay. Typically the pattern is one of three generations: the arriving generation speaks Spanish and learns only limited English. The first generation raised in America speaks fluent English and some Spanish. The third generation is completely immersed and fluent in English, speaking little to no Spanish.

Spanish in America: Language of the ghetto? | The Economist.