RICHARD R. GREEN, newly chosen to head the New York City public school system, has a plaque in his Minneapolis office that says, "No task will be evaded merely because it is impossible." He'll need the reminder as he sets about tackling a system notorious for its bureaucracy, its political infighting and its classic assortment of intractable educational problems: high dropout rates, low achievement and slummy buildings. The problems seem so daunting because the system is huge (968 schools in 32 community districts, several of which have more students than the entire school system Dr. Green ran in Minneapolis), and because it has withstood many earlier barrages of reform.

Yet Dr. Green's prospects are anything but grim. Longtime watchers of the New York system say this is the best opening in years for substantive change. His efforts will be followed with intense interest by more than just New Yorkers, since Dr. Green's challenges are magnified versions of everybody's, and if reform can make it there, as they say, it'll make it anywhere.

In Minneapolis, Dr. Green excelled at getting depressing, tumbledown school buildings transformed into orderly and inviting ones; at involving the business community in support for special programs; and at demanding achievement from poor and minority kids -- and getting it. In the new job, Dr. Green has the opportunity to put some serious money into New York's crumbling school buildings, since financier Felix Rohatyn recently agreed to make $600 million in municipal assistance bonds available to build new schools if a new agency were created to administer them -- and legislation to create such an agency is on its way to Albany. Likewise, the climate of enthusiasm nationwide for education reform and the fact that Dr. Green was the mayor's candidate for chancellor will stand him in good stead building bridges to the business community.

Most important is whether Dr. Green can haul more achievement and accountability out of a system whose scores are still low and whose dropout rate has been estimated as high as 50 percent. Here again he builds on solid efforts by some neighborhood school chiefs who have boosted scores in some of the poorest and most heavily black and Hispanic districts. Dr. Green, the first black chancellor of a system 38 percent black and 78 percent minority, rose from a tough background that included a stint at reform school. Hope for kids in many cities besides New York will depend in part on how many mountains he can move.