The Philadelphia School District should move quickly to fix flaws in the expulsion process of its zero-tolerance discipline policy.

The district had not expelled any students in the four years prior to Superintendent Arlene C. Ackerman's arrival. But officials recommended 156 expulsions last school year. An expulsion can last for up to a year.

The School Reform Commission recently voted to expel 65 students, and at least 25 cases are in the pipeline.

A "no-nonsense" disciplinary policy is long overdue in a school system where students and staff often feel unsafe. But a backlog in expulsion cases left dozens of students in limbo for months. That is unacceptable.

These lengthy delays deny students due process and can unfairly harm innocent students waiting for a hearing. If the system is ill-equipped to handle the high volume of expulsion cases, then it needs to be fixed.

A parent of an Olney West High School student said her son spent five months at an alternative disciplinary school waiting for a hearing in which he was eventually exonerated. By then, he had missed most of his senior year.

The Education Law Center says suspended students facing possible expulsion should get a hearing within 10 days. The district contends it is not required to meet that timeline. OK, but it has to do better than have students miss most of an academic year before their case is heard.

Ackerman says she is working on hiring more staff to speed up expulsion cases. With the new school year approaching, let's hope she has made progress.

In the meantime, the district can have some impact on its backlog by following policy guidelines that call for an informal hearing before an accused student is transferred to an alternative school. Of course, those students deemed a threat must be removed immediately.

But strict discipline is only part of the answer to make schools safer. Early intervention and services for students with chronic behavioral problems are also needed.