It is becoming clearer to America's politicians that this nation faces a grim challenge of truly educating children, especially poor and minority youngsters who have for so long been neglected.

New York Gov. Mario Cuomo, who insists that he is not a presidential candidate, called for a ''Decade of the Child'' last Wednesday, asserting that New York's children ''are threatened by poverty, inadequate education, even terrible physical and mental abuse. Their problems demand nothing less than a bold and broad commitment of government at all levels.''

Vice President George Bush, who is campaigning for the presidency, has dared to break with President Reagan publicly on one notable issue. While Reagan has fought for seven years to get the federal government out of education, Bush wants a greater federal role in enabling youngsters to read and write. Bush's wife is one of the nation's most influential advocates of the right-to-read and the need to educate all the children of America.

Sen. Paul Simon, the Rev. Jesse Jackson and several other candidates for the presidency are saying with both eloquence and anguish that this nation is in trouble unless it rises above racism and greed and makes quality education available to every youngster in the land.

Simply put, America is not competitive in the world markets, and soon may not be competitive in the military arena, because American leaders say ''ho hum'' to the realities that a disgraceful number of our teen-agers drop out of high school year after year, and a pathetic number of those who graduate cannot cope, let alone compete.

One reason for past political indifference has been the elitist notion that millions of youngsters are ''uneducable,'' or that the cost of educating them is prohibitive. It is noteworthy that New York City has just chosen as chancellor of its long-troubled public school system a black man who proved in Minneapolis that poor and minority kids can be educated without depleting the coffers of Fort Knox.

Dr. Richard R. Green was lauded by Minneapolitans as a ''Renaissance man'' who transformed the shame of that city, North High, into a proud symbol of achievement.

In his job in New York City, Green faces a level of racial and ethnic polarization, of individual irresponsibility, that he never knew in Minneapolis. Because Green knows how to work with white leaders, some blacks in New York will accuse him of being a ''puppet'' of white bosses. Some whites will fight him out of a belief that he got the job through ''reverse discrimination.''

Somewhere, at some time, some leader must arise with the force of conviction to say to all Americans that bigotry and parsimony are wrecking the American educational system. It seems clear that virtually all of the politicians of 1988 have rejected the ideology that education is not the business of the federal government.

Politicians of every stripe seem to have concluded that education is a line of America's defense that is every bit as important as megabuck missiles.

I personally am filled with doubts. I find it hard to believe that members of Congress and the White House will ever accept the idea that educating non-elite seventh-graders is as important to America's defense as buying Sergeant York guns.

But I'd sure like to be proven wrong.