Poverty, violent death and other key yardsticks show the 1980s were "a terrible decade for children," according to a new study on the well-being of American youngsters.

"The 1980s were a decade of deterioration for children," said Judith Weitz, coordinator of the Kids Count study produced by the Center for the Study of Social Policy, a Washington think tank.The study found a downturn in five of eight key measures of how children are faring:

-Child poverty worsened.

-Violent death among teens increased.

-The percentage of girls having babies out of wedlock went up.

-Juvenile incarceration soared.

-There was a slight increase in babies with low birth weight.

On the plus side, the percentage of teens graduating from high school increased, but only slightly. There also were sharp decreases in infant mortality and child death rates.

"This country fell behind or stalled on six key indicators of child well-being," Weitz said. "America's fate depends on how we treat our children today. We won't be ready unless we reverse these trends in the 1990s."

Data for all 50 states and the District of Columbia appear in the study. Vermont ranked first and the nation's capital last.

While black youngsters were highly likely to find themselves living in poverty, the study said, the 1980s marked a sharp increase in the percentages of white and Hispanic children among the poor.

The increase for white children was 36 percent, for Hispanics 31 percent and for blacks 16 percent.

Only four years ago, white children were far more likely than blacks to die violent or accidental deaths. But that altered sharply, with the black violent death rate climbing 51 percent, according to the study.

Nationally, the percentage of babies with low birth weight rose 1 percent from 1980 to 1988. Violent death among youngsters ages 15 to 19 increased 12 percent in the same period.