In Prince George's County, the magic number is 1,000. In Loudoun, it's 800. In the District, it's 450.

Those are some of the teacher-recruiting targets that public school officials are racing to meet this summer to fill classrooms in high-growth and high-turnover areas. Time is running out to staff local schools, some of which will start classes as soon as Aug. 22.

Yesterday, Catherine Casteel, a transplanted Nevada teacher, sped through a job fair in Greenbelt. After a five-minute credential check and a 10-minute interview, she landed an offer to teach middle- or high-school English for about $39,000 a year.

Casteel, 30, considered Fairfax, Prince William and Loudoun counties before settling on Prince George's. "They had a lot of job openings," she said. "I figured the odds of getting a job here would be better."

A little-noticed provision of the federal No Child Left Behind law is raising the stakes this recruiting season for school officials seeking credentialed teachers. By the end of the coming school year, the law requires "highly qualified" teachers in all core academic classes.

New data show that one-fourth of Maryland's classes this year did not meet that standard. That's an improvement: Last year, one-third of classes statewide fell short of the teacher-quality standard. Schools in high-poverty neighborhoods were far less likely than those in affluent communities to have highly qualified teachers.

Teacher-quality rules vary widely across the country, making interstate comparisons difficult. In Virginia, the latest data show nearly 95 percent of core-academic classrooms in 2004 had highly qualified teachers. D.C. school officials said no data were available.

"For the first time in a long time, there's serious competition among school districts to be able to hire highly qualified teachers," said Rep. George Miller (D-Calif.), a chief sponsor of No Child Left Behind. He has introduced a bill to spend $2.2 billion to help attract highly qualified teachers to high-need schools.

"If you don't get the teaching right, the rest of [school reform] is interesting but doesn't work," Miller said.

Across the Washington area, school administrators are recruiting heavily.

"It is a teacher's market," said Montgomery County schools recruiting director Thelma Monk, who is seeking about 200 instructors to meet a hiring goal of 800. "We woo and we coax."

Prince George's has held six job fairs, including yesterday's at Eleanor Roosevelt High School. The D.C. school system held one last week. Loudoun plans one for Saturday.

In addition, recruiters travel up and down the Eastern seaboard and make forays into the Midwest to find teachers. They also recruit heavily via the Internet and hunt for candidates from overseas. Specialists in mathematics, science, English as a Second Language instruction and teaching the disabled are in highest demand.

Fairfax schools held job fairs in January and February, locking in nearly 500 teachers with early contracts to help meet a hiring target of 1,300 instructional personnel.

"Our goal is to open school with every full-time vacancy filled," said Kevin North, assistant superintendent for human resources in Fairfax. "We're very confident we'll be able to do that. But it's a difficult market."

Schools in the District got an early recruiting jump this year, said Tony Demasi, executive director of human resources.

He said the system has placed 200 new teachers out of a projected need of 450. In the past, he said, District schools have scrambled in late July and August to hire teachers. Although a late hiring crunch in the District still might occur, Demasi predicted a smoother path this year.

"We've been hiring all spring long," Demasi said. "That's helped us immensely. We've been able to go out with offers much earlier than we had before."

For prospective teachers, the area offers broad opportunity. There are urban, suburban and semirural schools. There are high performers, underachievers seeking to move up and fast-growers. The cost of living is an obstacle, though, in a soaring housing market. Starting salaries for those with a bachelor's degree are $38,307 in Prince George's, $38,434 in the District, $39,600 in Loudoun, $40,000 in Fairfax and $40,542 in Montgomery.

The Prince George's job fair drew 300 candidates. Among 50 prospects in one orientation session were a special-education teacher from the Philippines; a fluent Mandarin speaker aiming to teach English as a Second Language; and a few would-be math and science teachers.

"If everything is in order, a lot of you will get some offers today," recruiter Robert J. Gaskin said. He said the system could train career-switchers who lack credentials. If vacancies are not filled in August, "we'll look at the other, best-qualified candidates," he said.

Dorothy Clowers, principal of William Paca Elementary School in Landover, said she was seeking six teachers: three for special-ed, one for pre-kindergarten and two for second grade. "I'm pretty desperate, but I won't just grab anyone," she said.

Clowers snapped up Felecia Wiggins, 44, a Bowie resident who has three children in public schools. Wiggins is leaving a law firm and accepting lower pay to be a pre-K teacher. She still needs to pass a teaching test and take some instructional courses.

"This is where I belong," Wiggins said. "I want the best for my children, and I want to give the best to other children."

Hillcrest Heights Elementary Principal Phyllis Hayes, left, interviews Kimberly Lindsey for an opening at a recruiting fair in Prince George's.