WHEN A STUDENT in a public school is charged with a serious crime, what immediate, automatic authority should the principal have to ensure peace on the grounds? In the past several days officials at three D.C. public schools have wrestled with separate incidents -- as well with some restrictive school system rules that existed until last Friday. But at these schools -- McKinley, Cardozo and Wilson -- both the confrontations and the system's responses were different. And even though the school board has just made a necessary change in its rules to allow involuntary transfers of students accused of crimes, still other steps -- including more sanctions -- should be considered to strengthen the hands of this city's principals.

At McKinley, six students were charged with selling drugs at the school; at Cardozo, a student was arrested and charged with selling drugs; and at Wilson, a student was charged with raping a classmate -- an incident that apparently did not take place on the school grounds. In all of these cases, the governing rule was that no student could be involuntarily transferred without receiving notice of the reasons, and each student had the right to a hearing. That may have been fine as far as students' constitutional rights were concerned, but what about everybody else at the school?

Wilson Principal Michael Durso took matters into his own hands. Announcing that he could not "in good conscience" allow the accused student at his school to remain there, Mr. Durso said he would stay away from the school to protest what he viewed as weak school policies; and he said he would not return if the accused rapist were allowed to remain at the school -- as ordered by a hearing officer last Tuesday.

With all of these cases pending, the school board called a meeting Friday and voted to give Superintendent Floretta McKenzie authority to transfer a student accused of a crime without first holding a hearing. She said that authority would be used in the McKinley cases, and that she had not decided what to do about the Cardozo student. In the Wilson case, the U.S. attorney's office yesterday dropped charges against the student; and though the corporation counsel still could prosecute the student as a juvenile, there has been no decision. At this point, the student is not charged with anything and is entitled to remain at Wilson; and Mr. Durso is expected back today, according to school authorities.

Clearly Mr. Durso chose to disobey the rules -- however popular his decision may have been among students, parents and teachers. But equally clearly, the issue he raised and the similar questions raised by authorities in the two other schools merited the emergency attention they finally got as well as the change in the rules. The school board should not wait for more emergencies before toughening up its rules even more. School board president R. David Hall said yesterday that the issue will be addressed -- including policies on expulsions and what the system should do with troublemakers once they are suspended, transferred or expelled. Every principal in town -- as well as the parents, teachers and students they serve -- has a stake in that response.