Some Philadelphia schoolchildren have gone an entire marking period without a permanent teacher. Others have multiple courses - in major subjects - without one.

Two and a half months into the school year, 136 teacher vacancies remain in the Philadelphia School District. Some of the jobs have been unfilled since September.

Both the district and the teachers' union agree: Combined with a substitute teaching situation that leaves hundreds of short- and long-term jobs unfilled every day, too many students lack stability in their classrooms.

"The effect on kids is huge," said Jerry Jordan, president of the Philadelphia Federation of Teachers.

Jordan attributes the problem to a management failure and to poor working conditions for teachers.

He and Arlene Kempin, the PFT vice president responsible for working with the district on human-resources issues, said they had never seen this many vacancies this late in a year - that in prior school terms, human-resources officials were by this point already focused on next year's hiring needs.

District officials disagree, saying that they have done their best to fill jobs in a tough situation, and that they are hampered by things beyond their control.

At this point last school year, there were 110 teacher vacancies among the district's 8,400-member teaching staff, district spokesman Fernando Gallard said.

"There is a challenge nationwide to find teachers," said Gallard. "We also have a school district that has been having several years of financial challenges, and that makes it much more difficult to attract teachers."

Gallard said the district was seeking state approval to use retirees to fill some vacancies. Twenty-nine retired teachers have offered to take open jobs.

"In the next few weeks, we'll be able to have a good number of these positions filled," he said.

In the meantime, a number of schools are scrambling to cope with vacancies both permanent and long-term, combined with daily substitute assignments that rarely are filled. (Source4Teachers, the firm hired to fill substitute jobs, managed to fill just 31 percent of open jobs Wednesday, a new high for the company, officials said.)

One school, Wagner Middle, presents an extreme case. Between vacancies and long-term illnesses, there are seven unfilled positions, according to the union.

One Wagner teacher, in an email sent to officials, said the "teacher shortage is destroying our staff, students, and the school. The staff members are being spread too thin."

Seventh graders cope with vacancies in most of their core subjects: reading, math, and science.

Teacher vacancies are affecting school climate, too, the teacher wrote.

"I believe the students are acting out due to the inconsistency of the educational environment," the teacher wrote. "This has also created a safety issue."

Wagner teacher Brad Berry said staffers are stepping up because they care about the students, but the vacancies are taking their toll. Teachers routinely must give up prep periods to cover classes.

"Urban schools are built on routine, and when the students just don't have a good routine, it upsets everyone," Berry said. "There are too many distractions and disturbances. People get burned out."

Gallard said the district does not take for granted the efforts of teachers left to fill in the gaps.

"We are grateful that we have teachers doing a tremendous job of covering classes," he said.

Grades for the first period were due Wednesday. Students who have had no regular teachers will still get marks, Gallard said, with the principal consulting with teachers who have covered classes to arrive at grades.