To answer your specific question, there is a quite long article by Roland Fryer at Harvard to explain where "race" differences in educational achievement in the United States began and what needs to be done to further narrow the divide.

http://www.economics.harvard.edu/faculty/fryer/files/Fryer_R...

The early situation during my lifetime is well summed up by a quotation from America in Black and White: One Nation, Indivisible

http://www.amazon.com/America-Black-White-Nation-Indivisible...

by Stephan Thernstrom and Abigail Thernstrom (which is a thoughtful book about the history of relations between the "white" majority and black Americans). Its description of public schools in the south sets the scene for today's legacy:

"The poverty of the South and the blindness of its planter-dominated leadership to the need for an educated labor force made the region the educational backwater of the country. School expenditures per pupil in Georgia in 1940, for example, were 42 percent of the national average; they were even lower in Alabama, Arkansas, and Mississippi. Those were figures for both black and white students; blacks of course fared worse than whites. Thus, in 1940, Alabama spent 3.2 times as much per pupil on whites as on blacks; Georgia 3.3 times as much; South Carolina 3.8 times as much; Mississippi a staggering 7.2 times as much. In the most heavily black counties of the Black Belt (so-called because of the exceptionally rich dark soil), per-pupil expenditures for black children were less than one-thirteenth of what was spent on whites. A pamphlet documenting such inequalities issued by the National Conference of Fundamental Problems in the Education of Negroes in 1934 observed wryly that 'if we assume the democratic principle of equal educational opportunity for all children, it would appear that it takes seven times as much to teach a white child as a Negro. As Booker T. Washington used to say, it is too great a compliment to the Negro to assume that he can learn seven times as easily as his white neighbor.'"

As that book points out, and as Roland Fryer points out in his more recent publication, today spending disparities are nowhere near that large (although they still favor "white" students in most jurisdictions), and now cultural factors and specific school practices are most at issue in the current divide. But the divide is narrowing, and has narrowed quite a bit in my lifetime, and there are identifiable improvements in United States schools that could make it narrow further.

On the language background of Americans, see

http://www.nytimes.com/2012/01/15/opinion/sunday/are-we-real...

for a recent report, based on the United States Census data, and an earlier Gallup Poll result

http://www.gallup.com/poll/1825/about-one-four-americans-can...

with different methodology. I had three grandparents, all born in the United States, who spoke a language other than English at home. The United States has long relied on immigrant families keeping their heritage languages (as in the case of my grandparents' families) to have people in the population who speak a language other than English. I have been a contract English-Chinese interpreter for the United States government and other clients. By test, I reached a high level of proficiency in a second language. But I would see highly proficient English in use among mixed groups of young people from other countries throughout the time I lived in Taiwan, and there is no comparable phenomenon of anywhere near as many Americans who grow up in English-speaking homes learning a second language of any kind. Singapore, by contrast, has four official languages from four different language families, has a population that spoke NONE of those official languages at home as recently as a generation ago, and yet has achieved good educational results in English (the sole medium of primary and secondary schooling) during my lifetime. Singapore is a very diverse country that has been more successful in getting good schooling results for that diverse population than the United States has. Similarly, repeating my previous comment here, my wife used a second language (Mandarin) to receive all of her schooling, and then learned a non-cognate foreign language (English) beginning in secondary schooling, and so is genuinely trilingual, a rare condition among Americans in her generation.