By October, Jill Imse's son already had been late 10 times to Avon Middle School in Avon, Conn. On a recent morning, she couldn't get him out of bed. Then came a call from the school.

It was the principal on the line threatening to send a police officer to the house. After that, Ms. Imse says, "he was in the shower pretty quick." He hasn't been late to school again.

Schools are starting to go to unusual lengths to get children to class on time. With attendance now an important measure in calculating performance and funding under federal and state laws, schools across the country are turning to both threats (like landing in the "tardy tank") and rewards (like movies and ice-cream parties) to attain punctuality. While schools long have battled tardiness among teenagers testing authority, the stepped-up efforts come amid signs that tardiness is worsening among younger students -- a symptom of the hectic lives children and parents alike lead these days.

To combat the problem, some elementary and middle schools are offering prizes for children who show up on time. Starting this year, Creekside Intermediate School in Dexter, Mich., is showing monthly after-school movies to students who stay punctual. Stone Creek Elementary School, Rossville, Ga., recognizes children with perfect on-time attendance by raffling off bicycles and computer-game consoles and hosting ice cream parties. Norwood View Elementary School in Norwood, Ohio, has begun awarding children a bag of popcorn on Fridays if they aren't tardy all week and meet other academic goals. And Lakewood Elementary in Euless, Texas, has a weekly raffle for students who get in on time. The prize reinforces the message: It is a watch.

Other schools favor the stick over the carrot. Starting this year, parents of any student who is late -- even just once -- at Garfield Elementary School in Mentor, Ohio, will receive a curt letter from the principal. So far, the letters have helped cut daily tardies in about half, to 12 from 25 in earlier years, Principal Ken Buckley says.

At Brinson Memorial Elementary School, in New Bern, N.C., students who are late to school are sent to "tardy tank" -- a separate classroom where they must wait until the next subject begins. "The kids go home and say, 'I don't want to go sit in that tardy tank,' " says Stuart Blount, Brinson's principal.

The crackdown comes amid evidence of an upsurge in late arrivals to school. According to surveys by the Department of Education, the percentage of public-school principals who reported tardiness to be a moderate-to-serious problem rose to 32.4 percent by 2000 -- the most recent year available -- from 24.9 percent six years earlier. The increase was even steeper for elementary-school principals: 27.1 percent reported it to be a significant problem, compared with 18.5 percent six years earlier.

States and districts don't usually keep statistics at a systemwide level, making it tough for policy makers to get a handle on the problem. Still, Marco Famiglietti, assistant principal at Avon, the school attended by the Imse family in an affluent suburb of Hartford, Conn., says the number of students tardy every day has increased roughly 20 percent in the past five years.

Mr. Famiglietti thinks part of the blame lies with all the technology available to children in their own rooms -- videogames, instant messaging -- that makes it easier for them to stay up past their bedtimes. At the same time, children have gotten busier as participation in extracurricular activities such as sports increases.

Some observers lay much of the blame on mom and dad. Ken Buckley, who retired from years in elementary education last year, only to take the helm at Garfield Elementary School this fall, says he has never seen so many children tardy to school as he has this year. He believes parents are absorbed by their own busy schedules.

The combined work hours of dual-earner couples with children has continued to increase over time, to 91 hours a week in 2002 from 84 hours a decade earlier, according to research by the Families and Work Institute in New York. Even traffic delays are worsening, according to some studies of large metropolitan areas.

Also spurring schools to action is the No Child Left Behind law. Under that 2002 legislation, schools could face a range of possible sanctions, including school restructuring and even dismissal of faculty, if students don't meet certain thresholds on state tests. "You can't teach children if they aren't there," says Susan Masterson, president of the National Association of Elementary School Principals, adding that elementary-school teachers like to begin their day with core academic subjects such as reading.

Besides test scores, the law requires schools to use another indicator of success. High schools use graduation rates, but for elementary and middle schools, attendance data often are key. Latecomers can potentially affect whether a school faces sanctions.

Attendance also is a big factor that states look at when calculating how much funding individual school districts get -- and it can be measured in the roll call taken at the beginning of the day. "There's a lot riding on tardies and attendance," particularly with slow growth in K-12 budgets in recent years, says Ken Seeley, president of the National Center for School Engagement, of Denver, which researches how attendance relates to student achievement. He says in a state like California, where districts receive funds based on average daily attendance, one student coming in late regularly could potentially cost a school thousands of dollars in lost funds.

Many schools say the new tactics have helped reduce tardiness significantly. At Lakewood Elementary, for instance, the "on-time watches" have helped reduce tardies to about 10 a day (out of about 600 students) from about double that previously, says Melinda Lineweaver, a counselor at the school. "Kids want to be part of that drawing," she says.

Tardiness crosses socioeconomic lines, affecting lower-income and affluent schools alike. Successful strategies focus on factors that can cause tardiness at a particular school. At Griffin Middle School in The Colony, Texas, where about one-third of students qualify for free or reduced lunch, Principal Cynthia Williams did away with bells and lockers starting last year. Bells encouraged too much "unstructured time" between classes, she says. She replaced the bells with teachers in hallways ushering students to their next class. And lockers fostered too much socializing, she says. She says the measures have significantly reduced lateness.

At Stone Creek Elementary, where about three-fourths of students are on free or reduced lunches, Principal Mike Culberson has even gone so far as to purchase alarm clocks for a handful of fourth-and fifth-grade students who are chronically late and show them how to set them. Through that, as well as "positive promotions" such as monthly raffles and ice-cream parties for kids with perfect attendance and no tardies for the month, student attendance records have improved tremendously. Before the "positive promotions" initiatives started two years ago there were about 20 tardies a day. Now tardies have dropped to about eight a day on average.

At the same time, Needham High School, in an affluent Boston suburb where 98 percent of graduates go on to college, this year is giving a day off to students who come to school consistently on time for an entire semester. The penalty before was a one-hour detention after five tardies. Now, says Principal Paul Richards, about 4 percent to 8 percent of students are late in a given day, compared with 8 percent to 12 percent in the past.

Another potent weapon has been forbidding students who were late to school to participate in that day's extracurricular activities, such as sports or clubs. After the upper division (grades nine to 12) at private Notre Dame Preparatory School in Towson, Md., tried that, the number of students late each day fell to only a handful from 12 to 20, says Christine Kaiser, director of student services.

"I wonder if the kids aren't a bit overextended," she says. "They're just tired, and it's hard to get out of bed in the morning."