The kids torment them. The permanent staff often ignores them. But America's corps of substitutes is vital - and spending more time with pupils than ever before.
Substitute teaching has been called the Rodney Dangerfield of occupations - it's a profession that just doesn't get any respect.
Students throw things, switch seats, pester for library or bathroom passes, or simply disappear out the door - never to return - when the sub's back is turned.
It's enough to make a substitute want to scrape his nails down the chalkboard.
"In the [armed forces], I taught classes of 500 men," says Leon Greenberg, who fills in for absent teachers in several northern New Jersey towns. "Believe me, it was much easier."
There's something about the presence of a substitute, an adult whom many children view as almost powerless, that can bring out the worst in a classroom. But with today's focus on standardized test scores, and a heightened recognition of the need to make the most of classroom time, many educators are urging a closer look at substitute teaching.
Students in the United States receive, on average, one full year of instruction from substitutes before graduating from high school, a recent study shows. But the quality of that instruction can vary wildly, influenced by everything from low pay to a lack of training for substitutes.
The challenge for educators is finding out what works and what doesn't - and figuring out how to tip the balance in favor of the former. To that end, the tales of substitutes themselves may suggest some places to start.
George Takis, a retired research engineer, particularly relishes rolling up his sleeves and diving into the challenge of teaching upper-level math.
He seldom struggles with a disciplinary problem. On the contrary, Mr. Takis says, the high school students he teaches in Fulton County, Ga., are generally glad to see him and eager to learn.
"I love the work," he says. "I wouldn't do it if I didn't."
A group of calculus students recently took him out to lunch to thank him for his teaching.
Many schools would love to replicate Takis's experience, but how? For every substitute who has a positive experience, there is another who can tell a tale of horror. One woman who asked not to be identified recounts abuses such as being bitten and spat at by emotionally disturbed children while serving in a classroom she was unprepared to handle.
Training can make an enormous difference, experts say.
Students say "they can tell right away whether the substitute is an educator or not," says Geoffrey Smith, director of the Substitute Teaching Institute at Utah State University in Logan. "Immediately they know if someone is comfortable in the classroom."
Many techniques that make the difference between success and failure can be taught, says Professor Smith. But few subs receive training.
In Utah, only about 7 percent of substitute teachers receive three or more hours of training before landing in a classroom, according to a study by the institute. Nationally, Smith estimates, the figure is about 10 percent.
But is better training enough to make up for what some in the profession say are deplorably low qualifications and even lower pay?
Utah is one of 28 states that require only a high school diploma to work as a substitute. Only two states - Oregon and Iowa - require teacher certification for their substitutes.
As for pay, it averages about $65 to $70 a day nationally. In some parts of the country, it's as low as $45 a day - about what a salon stylist would make for taking a few inches off the bottom of a customer's hair.
Despite the poor pay, unruly students, and lack of respect, substitute teachers with dazzling résumés are not a rarity in the nation's schools.
"We have among our workforce PhDs, college faculty, poets, scientists, military retirees - all kinds of people," says Shirley Kirsten, a concert pianist who works as a substitute teacher in Fresno, Calif. "When I was growing up in New York, the subs were often more interesting than our regular teachers."
Ms. Kirsten is frustrated, though, by a system that she says seems to work against subs rather than for them.
She remembers one of her own early experiences, when she was asked to teach math and science for 30 days in a troubled urban middle school. She arrived to find no lesson plans and no one to answer her questions.
"That was the experience that radicalized me," Kirsten says. She has since organized the National Substitute Teachers Alliance and is lobbying hard for benefits, minimum pay standards, and the establishment of professional standards for substitutes.
Ermalene Gault, a longtime substitute in the Gary, Ind., area, says it's common to step into a school and find no support.
The mother of five children, she knows how to discipline a group of children. She once faced down a boy who threw his desk at her.
But Ms. Gault worries that school systems have not yet grappled with a new reality: "It used to be you'd have a sub two or three times a year," she says. "Now kids have a sub at least an hour every day." Administrators and permanent teachers should show substitutes they are valued and help integrate them into the schools, Gault says.
Until about 18 months ago, districts everywhere were worried about an acute shortage of substitutes. With the turndown of the US economy, the shortage has eased in certain areas. In others, however, the crunch continues. Kelly Office Services of Troy, Mich., which began offering substitute-teacher placement services in 1997, estimates that on any given day, 10 percent of US classrooms are staffed by subs.
One way to minimize the amount of adjustment is to hire former teachers.
Patty Sue Haston, who taught for 42 years and now substitutes in McMinnville, Tenn., says she steps back into the classroom with pleasure. "I'd probably do it for nothing," she says.
Millie McBee, a former teacher who now subs in Apopka, Fla., also says she slips easily back behind the desk, but she thinks the profession doesn't offer enough pay and benefits to attract anywhere near the number of good workers it needs.
She teaches in middle schools about twice a week and says students are eager for a positive experience. "Sometimes I go into a school and the kids see me and ask, 'Are you going to be our sub?' and then give me big smiles when I say yes."
Ms. McBee also remembers a mother who sent a thank-you note and a gift because her daughter so enjoyed McBee's five days of teaching in her science class. "Those are the kind of warm-and-fuzzies that keep you going," she says.
When Dwight Tamanaha retired from his position as a US Air Force captain, he felt unsure about his future career and asked Kelly Services to place him in classrooms beginning in 1999. He now works as a sub on an Indian reservation in Wisconsin.
Despite tough experiences in the beginning (he recalls as a "nightmare" an art class filled with students carrying water guns), he stayed long enough to appreciate even the challenge of dealing with troubled kids. His military experience and his standing as a national champion weightlifter intrigue some high school boys, who are more apt to open up to him than to some of their regular teachers.
Mr. Tamanaha also has a unique classroom asset: He can "fly." Because of his extensive athletic training, plus an interest in Chinese exercises, he can lift himself up to six inches off the ground with one downward thrust of his outstretched arms.
It's a stunt the kids beg to see, so he often promises to perform it in exchange for good behavior and a productive class session.
"I might be the only sub in the US who does this, but it really works," he says with a laugh.
Christopher Gibson, a recent college graduate, moved to Santa Cruz, Calif., this summer and is still wading through the state testing required to begin subbing.
In the meantime, he's honing his skills as a substitute in a day-care center, where being "just a sub" has its advantages. Take the time when teachers limited playground activities and students organized a protest, complete with signs attached to popsicle sticks. Mr. Gibson was intended as the first target of the young picketers, but when they rushed on him, shaking their sticks, he quickly reminded them he had no authority whatsoever.
"That's right, he's only a sub," shouted a student ringleader, hurrying off to find a permanent teacher to harass.