Yeah you are 100% right. I probably am painting to rosey a picture. These illegals in our schools will probably get Americanized, become obese, get diabetes, and drop out. The good news is the Mexican family is shrinking dramatically. In the late 60s it was 9 now its 4. The Mexican middle class is finally growing, and that coupled with the shrinking family bodes well for a slowdown in immigration.
Impossible to get Americanized when the parents refuse (or can't) speak English at home. But slowing down the class because Julio can't understand advanced language will hurt Johnny. Basic English skills may get the kid a job, but the career will go to the kid who has a mastery of the language. Bilingual is better, but a basic knowledge of two is worse than a mastery of one.
Historically first generation immigrants do not assimilate into the American culture. The Irish kept speaking Gaelic, and the Slavs kept speaking slavic, and the Poles kept speaking Polish. The second generation tends to be bi-lingual, and third generation does not speak the legacy language at all.