During the second act of Massenet's opera "Cendrillon," a little girl barely four feet tall raced across the carpeted Kennedy Center Opera House lobby, from one end to the other, her head thrown back in absolute ectasy.

Inside, one girl crawled through the dark to the end of one aisle and, on all fours, read her program under the light on the carpeted step.

Two other girls, on their way back from the restroom, found only one seat -- so both slipped easily into it.

Several made better seats in the back row by sitting on the back ledge and propping their feet on the upturned seats.

In the foyer, five children were spotted lying down, like ducks in a row, shoes off, toes wiggling, watching the live closed-circuit TV picture of the opera.

Thursday was children's night at the opera, and 900 children -- including Amy Carter -- arrived for the lavish, 2 1/2-hour story of Cinderella. No parents were allowed.

If there was a lot of rustling inside the opera house, and a little confusion outside, it was all right. "They're quieter than a Friday night subscription audience," said Octavio Roca, a Washington Opera spokesman.

The children came from schools all over the area and from some embassies, chaperoned by 170 adult volunteers. Most at the event, sponsored by the Washington Opera Guild, hovered on the low end of the age spectrum. Amy Carter came with friend Cricket Keating and a Secret Service agent, all of which caused a mild stir.

"She's only a little kid," said one disdainfully to a friend who ran down the aisle to get a better look. "Her father just happens to be the president of the United States."

Adult volunteers maintained a fairly relaxed attitude. "I encouraged the kids to make themselves comfortable," said Grace Fleming, who found the group reclined on the floor in front of the closed circuit TV.

Some wrote letters to get tickets for the night at the opera in which they explained why they wanted tickets. ("I like music, particularly classical and other older types.")

They ran everywhere -- into the lobby, into the theater, up the stairs, down the stairs, out of breath, panting, racing. Girls ran, boys ran, everyone ran, usually in groups of two or more.

During intermission, they mobbed the concessions, treating candy with the relish adults usually reserve for fine wines. Once in their seats, they wrestled stubborn Jujubes out of the bottoms of candy boxes and traded away Junior Mints.

Before the opera began, director Brian Macdonald, a tall, thin man in jeans, gave the audience a brief introduction to the opera, telling them that he might occasionally stop it. "It's nice if you applaud sometimes," he said, "because that makes us sing harder."

Unfortunately, the audience took him at his word, and bursts of applause frequently broke out -- between verses of songs, after particularly strenuous dancing or stunning effects, sometimes after a run of particularly high notes. Finally, when it continued sporadically through the striking visual effects of the fairy godmother wafting through the air singing, Macdonald called out sharply from the director's table, "Please, quiet!"

Later, Macdonald amended his statement. "When the music finishes or when Mr. Bernardi (the conductor) holds up both hands, that's a good time to applaud."

Most in the audience were relieved to have an evening without the bother of parents.

"They're not here to boss us around," said Mark Dinan, 10, of Alexandria, "or tell us we can't buy candy."

Some were bored. "Those high voices kind of hurt my ears," said Kenny Lum, 11, of Bethesda, who along with friends Nancy Butsch and Monica Severino tarried a little before submitting themselves to the second act.

"My mother would have made me sit there and be quiet," said Severino with a grin. "She wants me to have culture."

"So does my mother," said Butsch, who plays the piano, "but I get enough at school."

At least one was a true veteran of musical events. Rene Phister, 11, is the son of Ralph Phister, a violinist for the National Symphony Orchestra. "Third stand, if you wanna be exact," he said, trying to contain a smile of pride.

"I've seen 'Marriage of Figaro,' 'Barber of Seville,' all that," he said, "and most of the ones my dad has done. I know my way around here pretty well. We had chaperones tonight guiding us around. But I went along with it anyway."