WITH LESS than two weeks to go before school resumes for its 166,000 students, the Philadelphia School District is looking for more than just a new chief executive.

Officials conceded yesterday that not all 153 teacher vacancies will be filled by the opening of school on Sept. 10.

Shawn Crowder, the district's vice president of human resources, predicted the year will start 50 to 60 teachers short, with many of the vacancies in the hard-to-fill positions of special education, Spanish, math and science at the middle- and high-school levels.

"While we have a lot of teachers waiting in the pipeline, they don't match up with our vacancies," said Crowder.

Of the 1,500 candidates who have been interviewed, half are teachers of the lower grades, which is not a need in the district, Crowder explained.

The district is working to get some of the candidates certified in the high-need areas, Crowder said, but in the meantime certified substitute teachers will be used.

Two schools will have interim principals for the first marking period, said Amy Guerin, a district spokeswoman. At Girls High School, longtime principal Geraldine Myles will postpone her announced retirement, Guerin said. And the Microsoft-backed School of the Future will be temporarily led by longtime district official Jose Lebron.

The teacher-vacancy problem is worse than it was at this time last year, according to data released by the district this week.

As of last Friday there were 153 vacancies compared with 134 at the same time last year. Crowder said the slight increase may be due to a new requirement of the federal No Child Left Behind law.

This year, special-education teachers who also teach core subjects in middle and high school must be certified in both special education and their subjects, she said. Last year they needed only a special-education certificate.

Education watchers decried the vacancies and said the district must do more to comply with the No Child requirement that every child be provided with "highly qualified" teachers in every subject.

"When there are vacancies at the beginning of the year, it creates huge problems for students - it's just chaos when they have a string of substitutes," said Eric Braxton, an official with the Philadelphia Student Union, an activist group. "And oftentimes, schools with vacancies become violence hot spots."

Jerry Jordan, president of the Philadelphia Federation of Teachers, said the vacancy problem is more pronounced than the numbers suggest, since most are in middle and high schools, where teachers have as many as five classes.

"We're talking about affecting the education of lots of children," Jordan said.

"The school district will put a substitute in a classroom who will not be with the kids all year . . . This means kids are the ones who will lose, because they are not getting the benefit of having a fully certified teacher in front of them."

Jordan also questioned whether the district is trying to save money by starting the year with an estimated 50 to 60 vacancies. Such "delayed hiring" would save the financially troubled district a substantial bit of money, he reasoned.

"Clearly it's a way in which they save money, but they save the money on the backs of the children," Jordan said.

Since last fall, district officials have been laying off employees and slashing programs to retire a budget deficit that once stood at $182 million and led to the early resignation of former district CEO Paul Vallas, whose replacement isn't expected to be hired until the end of this year.

Last week, interim schools chief Tom Brady unveiled a plan to slash $35.3 million more, leaving just under $20 million to cut.

Crowder denied that the district was intentionally leaving teaching positions vacant to save money.

"The goal has always been to staff schools with no vacancies," she said. "We are trying to pre-hire to make sure that teachers do not go to our competitors.

"We're trying to get people quicker." *