COOPERATION is critical on the domestic front, too. At all levels of government and community life, people battling drug abuse need to sharpen their efforts to eliminate what remains a national scourge.Statistics indicate progress has been made in recent years; the use of cocaine, marijuana, and other illegal substances has fallen among young Americans, according to surveys of high-school seniors. The federal government estimates that overall spending on illegal drugs has dropped from almost $50 billion in 1989 to a little over $40 billion now. But such figures are rough, and give only faint hope as the reports of drug arrests - well over a third of all inmates in the US have been convicted on drug charges - and drug-related violence mount. And the statistics miss some of the most vulnerable segments of the population, such as high-school dropouts. As with the drug production overseas, where coca-processing simply shifts around, so Americans' drug habits find new outlets. Police are particularly disturbed that heroin use may be surging. Raids have seized large amounts of that drug. Arrests and interdiction are indispensable. But the heart of the antidrug effort has to be to reduce demand. Treatment and education continue to get only about a third of the funds being poured into this war. That distribution of resources needs adjustment. To his credit, the new federal drug czar, Bob Martinez, seems attuned to this need. Ninety percent of schoolchildren in the US now receive some kind of drug-awareness education. But demand reduction has to reach further than the classroom. Most users of illegal drugs are adults. By some estimates, 76 percent are white and 68 percent are employed. In communities across the US, promising programs are underway. In the Dorchester section of Boston, for example, the Boston University school of social work is training local adults to counsel drug users in their neighborhood and help them escape the trap of addiction. The criminal-justice system is a crucial venue for identifying people with drug problems and making sure they get prompt and effective help, complete with follow-up monitoring - instead of merely being slapped into a cell. Programs that do this are taking hold in a few cities. Such efforts need greatly increased support from Washington to the grass roots. That's the path toward eventual victory.