One indicator of an immigrant group's ability to assimilate is the speed with which they depart from other poor groups and become as educated as the mainstream. Eastern European Jews, who came to America with nothing, reached average levels of education within a generation, and quickly surpassed by leaps and bounds the national average.
Mexicans were in the American Southwest before American settlers arrived, but most Mexicans have arrived here in the past few decades. Using General Social Survey data, I calculated the mean years of school completed for Mexican Americans born in the United States and compared them with black Americans.
I merged the 70s and 80s to get a sufficiently large sample. During that period, Mex-Ams were more than one year below the black mean. They made gains in the 90s, but dropped back in the past decade. In four decades, they have failed to reach the black level of education.