All good schools have certain marks. Two of them are: good principals and strong discipline. A good principal is absolutely critical to a school's success. And one of the fundamental duties of a principal is to ensure safety, order and discipline in his building. Without these conditions, learning will not take place.

It follows that a principal must have the authority to remove from the premises those who endanger the security of other students or who make impossible an orderly learning environment.

Recent episodes at some local schools, however, have led many parents here to ask the same question parents are asking elsewhere: Why don't principals have that authority?

Federal law is not to blame. It is true that in the last two decades or so the courts have established certain due-process protections regarding students' constitutional rights. But if some think these decisions prevent local officials from establishing effective discipline policies, they are mistaken. The federal courts' interpretations of the Constitution, as well as federal laws and regulations, almost never prevent a principal from expelling students or doing what is necessary to run orderly, disciplined schools.

The real obstacles, it turns out, may exist at the local level, where authorities often go far beyond the courts in curbing a principal's ability to remove a student. The reason is usually a concern that a school will be failing a child in the worst possible way if it simply sends him to the streets.

But this concern can be costly to the school. A few students can make it next to impossible for the rest to learn anything. The school will then end up failing many more children. In some circumstances, it can come down to a choice between removing a few or harming the many.

The street is no place for a child. But eroding a principal's authority and leaving him powerless to deal with an unmanageable student is no policy for a school. The answer may be a system that provides alternative schools for problem students.

Such schools exist and work; they are usually places where discipline is much sterner than usual. That may be exactly what a difficult student needs. In my judgment, state and local officials will find the best solution in systems that offer a greater variety of options for students with different problems and needs. But we must also face up to the fact that for some serious offenders -- those who are criminal in the real sense of the word -- the only solution may lie with the judicial system.

Good principals are men and women who hold forth a school's goals in ways that children and teachers can see every day. In the end, it is the essential task of a good principal to embody a sense of intellectual and moral authority for the entire school. Such principals must be supported and given flexibility to act. Only with that authority can they do the job we've asked of them: to run good schools.