Matt and Amanda Lewis came prepared to camp out on a chilly, damp night in the parking lot of Trinity Presbyterian Church in Arlington: There were snacks and water, movies and books, and a full tank of gas in their sport-utility vehicle.

Their goal? To be among the first to register their children -- 2 1/2-year-old triplets Matthew, Kate and Claire -- for the church's coveted, but scarce, preschool slots for classes beginning in September.

"This is how you have to survive to get your kids into preschool," joked Amanda Lewis, 31, who, alternating with her husband, would spend nearly 24 hours in the lot. "I'm almost embarrassed to have to do this."

It is a desperate measure that has faced not only the triplets' parents, but preschoolers' parents everywhere.

"There is a growing demand and a genuine lack of supply for high-quality preschool programs parents are seeking," said Mark R. Ginsberg, executive director of the Washington-based National Association for the Education of Young Children. "It's a national problem."

The shortage cuts across the socioeconomic spectrum; slots in the Head Start program for disadvantaged children are also hard to get. In the District, parents camped out for days to secure spots in public preschool programs and coveted elementary schools until the school system changed to a lottery system this year.

Many parents who gathered at Trinity said that at first they could not believe what they had to do to enroll their children.

When Kim Trundle's cousin told her last year that she had to spend the night in her car to get her child in the school, Trundle said she just laughed. "I said I would never do that," said Trundle, 35, as she sat in her SUV with two other mothers. "Now here I am."

Andy Jazwick, 38, expressed similar amazement as he and his wife, Claire, tried to register their son, Grayson. They seemingly were out of luck: They were 13th on the list for a program that had only 12 slots.

"I did this for Rolling Stones tickets," Jazwick said, "but I never thought I would have to do this for preschool."

Like any reality TV show, rules are quickly established as people compete for scarce resources. One mother who initially identified herself to a reporter repeatedly asked that her name not be used for fear that the six other preschools she applied to would think she had another option and shut her out. But the No. 1 rule is that no parents can leave after placing their names and license plate numbers on the church door's sign-up sheet. The unspoken consequence is that their name will be scratched off the list.

"There are supposed to be witnesses who check," Trundle said. But some people find ways around the all-night rule, by getting a nanny or a relative to sit in the car, for example. At Accotink Academy in Springfield, which will have its own camp-out tomorrow night, one mother was told that she would be taken off the list if she left.

But most parents honor the system by switching with their spouses to cover the long stretch. And Donna Garcia said she plans to rent a recreational vehicle to share with 10 other parents when they register their children for preschool at Accotink.

"The things we do for mom's night out," laughed Garcia, 37, who hopes to register her daughter, Peyton.

While most parents are exasperated with the lengths they have to go to, many feel that at least they have some control over the process, unlike a lottery.

"I don't mind doing this -- it's a wonderful school, and this way I have some control," said Heather Craddock, 31, who with her 2-year-old son brought a McDonald's meal to her husband, John, 34, who planned to spend the night at Trinity. "If it were a lottery, you have no idea if you'll get in," she added.

But even showing up in the parking lot for the night is no guarantee. "I'm going to spend 20 hours here to be on a waiting list," complained Barbara McGowan, who wanted to register son Aidan. "This is for preschool. I don't know what's going to happen when he's ready for college."

But there will be no future camp-outs at Trinity: Gwen Brown, the director of the school, said it will switch to a lottery system.

"With this year being as cold as having been, the thought of people spending time in the parking lot, I thought this is crazy," Brown said. "I don't want parents to have to spend the night."

And as the night progressed on Friday, the dim glow from DVD players eventually faded as many of the parents went to sleep under the blankets they brought.

The next morning, they gathered in line, looking relieved to begin the sought-after registration process. While the women looked refreshed -- most had gone home while their husbands did the hard duty -- many of the men were unshaven and had "bed hair."

A sleepy-looking Mike Egge, who spent the night to register his 2-year-old twins, Olivia and Luke, raised his fist in the air with accomplishment as he completed registration.

"They better get into Harvard after this," he said as he strolled down the hall.

Parents register their children at Trinity Presbyterian Church in Arlington for preschool programs. From left are Maria Puletti, daughter Alex, Laura FitzPatrick, Mia Puletti and, at desk, Erica McCullough. Behind her is Gail Wentzell.Stacy Hallett camps out in her car in Trinity's parking lot for the chance to register son Conor. Once parents sign up, they can't leave the waiting area.