''The first three months were incredibly difficult,'' says her mom, Robyn Ann Kreusel of Dacula, Ga., a part-time nurse. ''She was 5 years old - it was pure exhaustion going for that number of hours.''

Kreusel's decision to enroll her daughter in a full-day kindergarten class is part of a national trend. The longer school day is useful for working parents, and kids who already have spent a couple years in preschool are used to the routine.

Proponents point to several studies that show children in full-day programs have more opportunity to master today's tougher kindergarten curriculum.

Still, other parents continue to embrace the traditional half-day kindergarten and the extra time it gives kids at home before they head off to first grade.

''They're still little,'' says Karen Kilroy, 37, a stay-at-home mom in West Chester, Pa. When kids are in school all day, ''you get them in the morning when they're grumpy and at dinner time when they're grumpy, and you're missing the fun time in between,'' she says.

Kilroy's school district offers both full-day and half-day options, but many parents don't have a choice.

Nationwide, more than 60 percent of children in public or private kindergarten were enrolled in full-day programs, the 2000 U.S. Census indicated. Many Utah school districts offer extended-day kindergarten, but parents don't have to send their children, said Brenda Hales, state associate superintendent. Utah Gov. Jon Huntsman Jr. signed a bill in 2007 that allocated $30 million to expand optional extended-day kindergarten programs for at-risk children.

Nine states mandate that full-day kindergarten be offered, and two - Louisiana and West Virginia - require that kids be enrolled in it, according to a 2005 report from the Denver-based Education Commission of the States, a nonprofit focused on school reform.

Many communities, on the other hand, don't have the money or space to offer full-day kindergarten. Kathy Swegles, who teaches two three-hour kindergarten classes a day in Northville, Mich., wishes full-day were available.

''A lot of kids are going full day anyway, doing child care the other half of the day. They might as well be in an academic environment rather than just child care.''

Kreusel, the Georgia mother, was impressed with how much her daughter learned in full-day kindergarten.

''I never expected my child to be writing three-sentence paragraphs or reading by the end of kindergarten. I never knew that was an expectation of kindergarten,'' says Kreusel, 32. ''The kindergarten curriculum is very difficult.''

Kilroy says her daughter, Emma, who attended half-day kindergarten, also was well-prepared for first grade.

''Academically she got everything out of kindergarten that I expected she'd get out of it,'' says Kilroy. ''She was close to reading at the end of kindergarten. It clicked completely at the beginning of first grade.''

Regardless of how many hours children go to kindergarten, parental involvement is key, says Swegles, who has been teaching kindergarten for 11 years.

''You have to keep the parents well-educated and informed of what you're working on so they can continue at home,'' she says.

Kreusel thinks the adjustment to a longer day is just tough, whether it happens in kindergarten or first grade.

''The question is, what age is the right age to make that transition?'' she says.

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* Tribune reporter LISA SCHENCKER contributed to this story.