ST. LOUIS is your classic hard-case school desegregation city: 80 percent of its school population is black and most of the suburban school districts are white. After years of litigation over how best to integrate schools in the area, a settlement has been proposed to the federal court. The NAACP and the city school board have signed the proposal as have almost two dozen suburban school districts. The objective of the plan is to encourage the voluntary transfer of black students from the inner city to suburban schools and to provide incentives for white students to go to special magnet schools in the city. Suburban schools have agreed to increase black enrollment by 15 percent or to a total of 25 percent, whichever is less, during the next five years. For their part, the city schools would provide enriched programs, new specialty schools, creative early-education classes and other facilities designed both to attract suburban youngsters and to improve those city schools that will probably remain predominantly black. The key to the agreement is providing incentives that will lead to voluntary interdistrict transfers.

All this will cost money, of course. The parties to the agreement propose that the state of Missouri redistribute state aid and pay all transportation costs and that the city of St. Louis raise school taxes. Both state and city governments have thus far refused to accept this aspect of the settlement. But neither of the alternatives to a voluntary plan --continued racial segregation or mandatory court- ordered busing--is really practical.

If the St. Louis proposal is adopted and put into effect, other cities will have a chance to see if imaginative voluntary programs will work. Spending this money makes sense. In the long run the construction of such a useful model would be far less costly --financially, emotionally and socially--than continuing the bitter and divisive struggle over school desegregation.