Yet another familiar school-days object may be going the way of the inkwell and the slide rule.

Encouraged by a milk industry study that shows children drink more dairy when it comes in round plastic bottles, a growing number of schools are ditching those clumsy paper half-pint cartons many of us grew up with.

Already more than 1,250 schools have switched to single-serving bottles. While that is still a tiny fraction of the nation's schools, it is a significant jump from 2000, when there were none, according to the National Dairy Council.

"Those square containers are awfully hard for kids," says New Hampshire Agriculture Commissioner Steve Taylor, who has watched the trend spread to some 320 schools in New England. "Teachers say you can spend the whole lunch period just walking around and opening those containers."

Though plastic long has been the favored packaging for soda and other drinks, schools sought bottled milk only after a 2002 Dairy Council study found milk consumption increased 18 percent in schools that tested bottles. The study also found that children who drank bottled milk finished more of it.

The change to plastic brings schools closer to overall milk packaging trends. In 2001, more than 82 percent of the nation's milk was packaged in plastic, up from 15 percent in 1971, according to the U.S. Department of Agriculture.