Yet another school-day icon may be going the way of the inkwell and 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 you grew up with.
Already more than 1,250 schools have switched to single-serving bottles. While still a tiny fraction of the nation's schools, it's a significant jump from 2000, when there were none, according to the National Dairy Council.
But it's not only increased consumption that has schools asking the paper or plastic question.
"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," he said.
Though plastic long has been the favored packaging for soda and other beverages, schools only sought bottled milk after a 2002 Dairy Council study found milk consumption increased 18 percent in schools that tested bottles.
The change to plastic brings schools closer to overall milk packaging trends. In 2001, 82 percent of the nation's milk was packaged in plastic, up from 15 percent in 1971, according to the US Department of Agriculture.
That's good news for the environment. Dairy officials say the waxed paper used in milk cartons is difficult to recycle, but the plastic bottles are among the easiest of substances to recycle.
While the growing use of bottles in schools can partly be attributed to ease -- educators say plastic caps are easier for children to open, and round bottles fit better in their hands -- marketing savvy deserves at least as much credit.
Several years ago the milk industry decided its somewhat pedestrian boxes weren't visually competitive when sold alongside the relatively attractive bottles of juice and soda that were increasingly common in school cafeterias.
It was a matter of making milk as interesting as other drinks, and giving children the same options they have outside of school, says Grant Prentice, executive vice president of marketing for the Dairy Council.
Many schools even display the bottles in glass-front upright coolers -- just like at the convenience store -- and obesity concerns have prompted schools around the nation to oust soda machines in favor of milk vending machines.
Though bottled milk costs schools more, Prentice says high schools that served it during the study saw lunch program participation rise 5 percent. And by some accounts the study underestimated the growth potential.
The milk industry also likely will benefit. Though Americans have been consuming less milk steadily since the 1970s, dairy officials hope reversing that trend for children will result in a lifetime of drinking more milk.