School officials across the Washington region have filled most of their teaching jobs this summer, one of the busiest recruiting seasons in recent years, but they still will need to staff a few hundred classrooms with substitutes when school starts next week.

Each of the districts has fewer than 90 vacancies remaining, primarily in subjects that traditionally have been difficult to fill: math, science and special education, officials said yesterday. Public schools in the District, Prince George's, Howard, Anne Arundel, Charles, Calvert and Loudoun counties open Monday. Classes begin Wednesday for Montgomery County students, and after Labor Day for most Virginia schools.

A large wave of baby-boomer retirements amid a national teacher shortage has created a record number of job openings in several districts, prompting school administrators to intensify their hiring efforts this summer.

More affluent school systems such as Fairfax, Montgomery and Howard generally filled their vacancies earlier, even picking up a few teachers from Prince George's, where annual salaries can range $2,000 to $5,000 less.

But Prince George's launched one of the largest and most critical recruitment efforts this summer, hosting two summer job fairs locally and making a half-dozen extra out-of-state recruiting trips. The district also sought to draw teachers out of retirement by offering full salaries without jeopardizing pensions. But officials said they still were forced to hire 440 provisionally certified teachers to help fill their 1,400 openings. The system still has 89 vacancies.

New Prince George's School Superintendent Iris T. Metts had directed her staff not to hire provisionally certified teachers, but about 225 had been offered contracts before she arrived July 1, said acting personnel supervisor Eleanor White. The rest were hired to fill "critical-need" jobs in subjects for which fully certified candidates could not be found, she said.

Provisionally certified teachers lack either some college courses or a passing score on the National Teachers Exam or both.

White said that the number of provisional teachers Prince George's has hired is still high but that the system's record has improved from last summer, when it hired 728 provisionally certified teachers.

Overall, about 18 percent of Prince George's 8,000 teachers last school year were provisionally certified, the highest percentage in the state. Officials say they have not tallied the total number of provisional teachers for this school year.

"The state does want us to lower it, but we've already made a dent. Next year we'll go after it again," White said. "Right now, the foundation is weak, and we're restoring the foundation. I never believed I could do a quick fix."

A number of experienced teachers left Prince George's for better pay in nearby districts, including Montgomery County, which hired about 100, according to Montgomery Personnel Director Elizabeth Arons.

Montgomery has filled all of its 1,000 openings with fully certified teachers, officials said. More than 50 teachers who retired from Virginia districts are coming to Montgomery to teach, enabling them to draw both a Virginia pension and a Maryland salary. "Many are in their early fifties, and they have a lot of years left in them," Arons said. "We call them double-income earners."

But Arons said Montgomery was not poaching from other jurisdictions.

"If you don't recruit anywhere and someone sends in an application, how could that be called poaching?" she said. "They're in our applicant pool. It's only good business to consider the best ones. We recruit at college campuses, not other school districts."

Howard County school officials said they took about 21 teachers from Prince George's to help fill nearly 500 openings, about 200 more than last year. Howard still has about 20 vacancies.

Anne Arundel County also had about 500 openings and has 50 left to fill. Administrators went to 82 job fairs or colleges, about twice the usual number, because the recruiting climate was so much more competitive, officials said.

"We spent a lot more energy going to more sites and developing marketing materials that we never needed before, such as a display board and video," said Sharyn Doyle, Anne Arundel's supervisor of teacher personnel.

In Charles County, school officials reported 23 teacher vacancies remained yesterday, while Calvert filled the last of its 100 openings this week.

The D.C. public school system hired 1,100 new teachers and had 35 remaining vacancies, Superintendent Arlene Ackerman said earlier this week. About 350 of the city's 5,100 teachers are not certified, down from 1,200 a year ago.

Among Northern Virginia districts, only Loudoun County starts classes Monday, and officials there say they have filled all but a half-dozen of their 450 vacancies.

Fairfax County schools do not open until after Labor Day, but officials there say they have hired about 1,300 teachers and expect to fill the remaining 100 positions before the first day of classes.

Even in Fairfax, where high salaries traditionally have been a strong draw for teachers, officials had to make a more concerted recruiting effort this year. For the first time, Fairfax held its own teacher and guidance counselor job fair, which it advertised through the Internet.

"This will be a record-breaking year for Fairfax," said Kevin North, the school system's director of employment. "We have 300 more teachers hired than we did last year, and last year was a record year."

Staff writers Brigid Schulte, Liz Seymour and Nancy Trejos contributed to this report.