Philadelphia School District Superintendent Arlene Ackerman's attempt to highlight high numbers of teacher absences at some schools backfired when letters of caution also mistakenly went to educators who were out for serious illnesses and those who missed as little as a day.

Upon her arrival in June, Ackerman said she was dismayed to find "alarming numbers of teachers out" at some schools and an absentee rate hovering at 8 percent.

Teachers who regularly call in sick disrupt learning in a district where many students still score below basic levels on reading and math tests, she said.

Ackerman said she decided her first step would be to send letters to teachers with 10 or more absences last school year - not including those with serious illnesses or on long-term leave. The letters, dated Dec. 5, urged teachers to try to attend unless it "is completely unavoidable" and noted how many days the teachers had missed during the last school year.

She wanted them sent in September, she said, to set the tone for good attendance at the start, but was dismayed to learn last week that the letters had not yet gone out.

And things only got worse when they did.

"I'm just really sorry. It was never intended to cause the kinds of problems that it caused," Ackerman said in an interview yesterday afternoon. "I don't know what happened, but I'll tell you heads are rolling."

She said she already apologized to principals and was sending a letter of apology to teachers.

The phones lit up at Philadelphia Federation of Teachers offices earlier this week when teachers began receiving the notices at home, said Jerry Jordan, president of the union, which represents more than 10,000 teachers. Letters were sent to 8,400 teachers who had one or more absences. They should have gone to fewer than 1,000 teachers, although officials could not give the exact number.

"There was nothing humane about this," Jordan said, noting that complaints were particularly strong at one school where a staff member dealing with pancreatic cancer got a letter.

"It certainly has really served to anger people and make teachers feel disrespected."

One 37-year-veteran who is so angry that she declared she would retire complained: "Teachers with one day of absence get a letter? That's outrageous!"

George Panrock, a history teacher at Martin Luther King High School, said he missed 10 days last year because of a serious foot infection that required him to have surgery and spend time in a wheelchair and on crutches.

"I had a hole in my foot and I was there every day except 10 days when I was getting this looked at," he said. "I had a letter from my doctor, stating I was seeing him for all the days I was out."

He complained to the union when he got the letter.

"I was pretty mad," he said.

The letters from the district were signed by Andrew M. Rosen, executive director of employee relations. Rosen did not return a call for comment yesterday.

Under the union contract, teachers get 10 sick days and can carry them over each year. They are reimbursed for 25 percent of unused sick time when they leave or retire.

Union officials said many teachers accumulate a lot of days, meaning their attendance is very good.

Jordan asserted that a better way to handle attendance problems is to have principals - who know individual circumstances - meet with teachers. That's what was done in previous administrations, he said.

Ackerman also directed that the 1,900 teachers with perfect attendance be sent letters of congratulations.

But that went awry, too.

"Some people who didn't miss a day didn't get a commendation letter," she said.

District officials would not pinpoint last night which schools had large numbers of teacher absences.

Ackerman said that despite the errors, she still would press teachers for good attendance.

"I'm really serious about holding adults accountable about coming to work," she said. "I'm not saying I want people to come when they're sick . . .. When you can, we'd like you to give us the best you have."