The city sent letters to the parents of more than 5,000 frequently absent students today, urging them to make sure their children come to school in September.

When school starts, phone calls will follow the letters, Mayor Bloomberg said today, describing the first fruits of the interagency task force on chronic absenteeism he convened in June.

Following the task force’s recommendations, the city is launching a campaign to boost attendance among the most absent students at 25 schools. Bloomberg announced the campaign, called “Every Student, Every Day,” today at Brooklyn’s PS 345, where 91 percent of students attended on average last year.

The city’s 90.74 percent average attendance masks the fact that 20 percent of students missed more than 20 days of school last year, Bloomberg said. That figure was first reported by Center for New York City researchers in a 2009 report that called on the city to marshal the efforts of city agencies and community groups.

The 25 schools participating in the Every Student, Every Day pilot will assign volunteers from programs such as City Year, Citizen Schools, and Learning Leaders to mentor the most frequently absent 1,500 students. They’ll also host special attendance-focused parent meetings early this fall. The schools were selected both because they have high numbers of chronically absent students and because they have strong, stable leadership, Bloomberg said.

The city will also share attendance data among parents, attendance mentors, and community groups working with schools. And it will get agencies other than the Department of Education involved when non-academic issues, such as health, substance abuse, or homelessness, appear to fuel absenteeism. For example, 15 shelters are getting attendance liaisons who will receive weekly reports on the attendance for the 1,100 students living in them.

“We need to pool the resources and talents of every city agency and community partner,” said John Feinblatt, an advisor to the mayor who headed the task force.

The mayor didn’t say how much the project would cost. The city cut a $1.4 million anti-truancy program last year.

Enterprising principals have tried many of the initiative’s strategies before. Sheepshead Bay High School (attendance rate: 81 percent) holds mentoring sessions for students with poor attendance, said Principal Reesa Levy.

But Levy said with more volunteers, she could reach more students. “There are issues outside the building that these people can handle for us,” she said.

Noting that three-quarters of sixth-graders who are chronically absent never graduate from high school, Bloomberg emphasized that the goal of the truancy initiative is improved school performance. “We’re going to see that this translates into greater performance for these kids, and that’s what it’s all about,” he said.

One thing the city won’t be doing to improve attendance is change regulations so that it’s required for promotion. Currently the city does not require students to attend school a certain amount of time to be promoted. Asked today whether that could change, Klein demurred.

“If a kid has mastered the work … I don’t want to not promote that child,” Klein said.

The schools participating in the pilot year:

Isaac Newton Middle School for Math and Science, Manhattan
PS 48, Bronx
Ps 75, Bronx
MS 301 Paul Dunbar, Bronx
The Hunts Point School, Bronx
IS 219 New Venture School, Bronx
PS 111 Seton Falls, Bronx
MS 571, Brooklyn
PS 81 Thaddeus Stevens, Brooklyn
MS 584, Brooklyn
PS 13 Roberto Clemente, Brooklyn
PS 149 Danny Kaye, Brooklyn
PS 345 Patrolman Robert Bolden, Brooklyn
PS 329 Surfside, Brooklyn
PS 181 Brookfield, Brooklyn
Albert Shanker School for Visual and Performing Arts, Queens
PS 14 Cornelius Vanderbilt, Staten Island
IS 49 Berta Dreyfus, Staten Island
Marta Valle High School, Manhattan
Jane Addams High School, Bronx
Sheepshead Bay High School, Brooklyn
Bronx Expeditionary Learning High School
High School for Teaching and the Professions, Bronx
School for Legal Studies, Brooklyn
Richmond Hill High School, Queens