When 15-year-old Jess Harrahill heard a gruff male voice summon him twice from behind a car tucked back in a private driveway, a frightening possibility flashed through his mind: "Somebody's going to beat me up," he thought. But when the Monrovia, Calif., homeschooler-on his way home from adjunct classes at the local high school-identified the speaker as a police bicycle officer, he realized the police were just rounding up the usual suspects.

During the 1996-97 school year, police detained and questioned Jess Harrahill and his 13-year-old brother Ben-Joe a total of 22 times under Monrovia's truancy law, an ordinance that doubles as a de facto daytime curfew. Monrovia, a city of about 38,000, is among a growing batch of American burgs with truancy and daytime curfew ordinances in effect. As of December, according to the U.S. Conference of Mayors, 76 cities enforce daytime curfews; still more are considering imposing them. Such laws authorize police to detain, question, and cite on public property during school hours anyone who appears to be under age.

School and law enforcement officials credit the curfews with driving down truancy and juvenile crime. But the Home School Legal Defense Association (HSLDA), ACLU, and other watchdog groups believe such edicts erode constitutional freedoms. "Daytime curfews reverse the long-held American presumption of 'innocent until proven guilty' and preempt the constitutional right to move about freely," says Michael Farris, president of the Home School Legal Defense Association. "They're sold as a feel-good strategy, but really are a curtailment of liberty that produces no benefits."

At least 14 cities, including San Diego and Washington, D.C., have faced constitutional challenges to nighttime curfew laws. On behalf of the Harrahills and four other families, HSLDA filed suit in May 1997 questioning the constitutionality of Monrovia's truancy ordinance. In Washington and San Diego, nighttime curfews were struck down; the Harrahill suit may be a national test case for daytime curfews.

HSLDA's case also seeks to debunk the city's statistical claims of success. Monrovia police officials claim the daytime curfew contributed to a 54 percent decline in the school district's dropout rate during the 1995-96 school year. But the California Department of Education has a different story: Its annual report for the same period pegged Monrovia's dropout rate at 3.3 percent, an increase of more than a third over the previous year.

Roger Johnson, a Monrovia police captain, says his curfew-backing statistics have been verified by the Rand Corporation, a California-based think tank. City officials feel the city's truancy ordinance stands on solid statistical and legal ground.

"We've taken an education code that required truants to be handcuffed and taken into custody, and actually made it less intrusive on kids," says Mr. Johnson. He says the city's newer truancy procedure, passed by its city council in 1994, empowers police to question and cite kids who can't satisfactorily explain their presence on public property during school hours. Offenders must then appear in juvenile traffic court accompanied by a parent. "We're concerned for the community's kids," says Johnson.

But Jess Harrahill's mother Rosemary, who says crime and truancy levels in Monrovia don't warrant the amount of police-child contact generated by the truancy ordinance, calls the law "heavy-handed." Ironically, Monrovia is a favorite of Hollywood filmmakers for location shots requiring a Leave It to Beaver neighborhood feel. Films like Beethoven (boy meets rambunctious but endearing St. Bernard), and TV series like Picket Fences are routinely shot on the city's hospitable streets. Crime rates, which are relatively low for the L.A. basin, validate the city's small-town reputation.

So does Monrovia really need a law that authorizes police to clear kids off neighborhood streets? "Every community needs to be concerned with children attending school. You don't need to have a big crime problem to perceive that something needs to be done," says Mr. Johnson.

Mr. Farris says that job should be left to schools and parents. He says other, less restrictive methods like school attendance monitors can achieve the same objectives without impinging on the rights of homeschool and private-school kids, who are often on city streets during school hours due to varied class schedules.

According to Mrs. Harrahill, a full-time mom who has homeschooled five kids, Monrovia police seemed at first to be willing to work with families negatively affected by the truancy law. But she says her repeated attempts to familiarize police with her children failed to decrease the number of times police stopped her kids.

One overture by Monrovia police did attempt to ease the truancy law's impact on home- and private-schoolers: According to Mrs. Harrahill and deposition statements by pastor John Waldrip, a witness in the HSLDA suit, police chief Joseph Santoro offered to issue bright orange I.D. cards to kids whose schedules varied from that of the city's public schools. "It's a police-state mentality," says Mrs. Harrahill: "Innocent,