The percentage of new teachers in New York City public schools who are black has fallen substantially since 2002, dropping to 13% in the last school year from 27% in 2001-02, city figures show.

The change has dramatically altered the racial makeup of the new teacher workforce, which last year included about 400 more white teachers than it did in 2002 and more than 1,000 fewer black teachers.

The overall teaching force has been less affected: Black teachers made up 20% of the workforce in fiscal year 2008, down from 22% in 2001, while the percentage of white teachers has stayed constant at 60%.

The changing demographics come in a school system that is increasingly made up of non-white students.

Educators and advocates said they have been troubled by the data for several years — and they said they are especially troubled this year, the 40th anniversary of the Ocean Hill-Brownsville crisis, in which black community leaders challenged the city to make school staff more representative of the city.

“We want a school system that values educators who are invested in their students and who reflect the communities of which they are part,” a member of the Center for Immigrant Families in uptown Manhattan, Donna Nevel, said.

The Department of Education’s executive director for teacher recruitment and quality, Vicki Bernstein, said responsibility for the declining diversity lies with a state requirement that all public school teachers be certified by 2003.

The requirement was introduced in 1998, forcing the New York City public schools to scramble; before 2003, 60% of new teacher hires were uncertified, and 15% of the overall teaching corps in the city was not certified.

School officials said the mandate had a chilling effect on diversity, because the state certifies very few black teachers. According to a state report, in the 2006-07 school year, black people made up just 4% of new certified teachers who identified their race.

Ms. Bernstein said that she joins educators who are concerned by the trend.

Since last fall, she said she has made recruiting black and Latino teachers a priority for her staff. She convened a working group to plot ways to raise the city’s figures.

She said her strategies so far include visiting historically black colleges to recruit possible teachers; publishing advertisements that focus groups show appeal to black and Latino applicants, and making a concerted effort to follow through with those candidates as they make their way through the application process.

The city has also halted a program to recruit teachers from outside of America and kicked off an initiative to attract teachers who themselves attended city public schools, by offering a special award to new recruits who are city school graduates.

The 50 recipients of the Gotham Graduates Give Back award receive a $1,000 stipend before the start of the school year and are featured in recruitment materials.

“This is a high priority for us,” Ms. Bernstein said. “We’re looking at it across every level of teacher recruitment.”

The techniques were more aggressively instituted in recruiting for the group of teachers who earn certification while teaching, the Teaching Fellows, Ms. Bernstein said.

Those results are showing up. In the 2006-07 school year, 32% of fellows were black or Latino. This year, 37% were, school officials said.

Teaching Fellows make up between 20 and 25% of new teachers in the city, Ms. Bernstein said.

The president of the teachers union, Randi Weingarten, said the city should consider another move: encouraging people who are already working in the school system but not as fully certified teachers to become teachers.

“I never want to see the mistakes that were made in the ’60s and the ’70s,” Ms. Weingarten said. “Just in watching, in being at new teacher events in the last few years, and in just scanning the crowd, I’m really, really concerned.”