Prudent parents tell their children that in the real world, things are often not what they seem. This term, the Supreme Court compellingly illustrated that homily by assuring public school students that they, like all Americans, are protected by the Fourth Amendment. At the same time, the court, turning into an illusionist, took away the essence of this newly secured protection so that, as Justice John Paul Stevens said in dissent, the Fourth Amendment may now be "virtually meaningless in the school context."

What the court has done is to set a lower constitutional standard by which administrators and teachers can conduct full-scale searches of students. Outside the school, such searches have to be based on "probable cause" -- the cop must know of facts and circumstances that would lead a careful man to believe that a criminal offense has been committed and evidence of it can be found at a specific place. But inside the school, all that is required now is that school officials have "reasonable grounds" for suspecting that if they shake down the student they'll find some evidence that the rules of the school or the laws of the land have been broken. Almost any educator can rattle off dozens of "reasonable grounds" before even seeing the first student of the day.

Justice William Brennan, who keeps striving valiantly to remind his brothers and sister what the Fourth Amendment actually says, pointed out in his dissent that the crucial words "probable cause" practically leap out at the reader of the Fourth Amendment. Nothing less would do for the architects of our liberty, who remembered that British troops had only recently been crashing through their doors in the full belief that they had "reasonable grounds" to search at will.

There has been much commentary about this school search case, New Jersey v. T.L.O., with school administrators, heads of teachers' unions and other curators of the young expressing gratitude to the court for recognizing that school is a special place with special disciplinary problems. Even the American Civil Liberties Union has reacted quite mildly to the 6-3 decision. A lawyer on the national staff, Carl Loewenson Jr., said: "We had hoped the court would give students the same protection that all citizens have, but the Supreme Court seemed to be looking at how things operate in the real world. School administrators don't walk around with copies of the Constitution and the latest court decisions in their hip pockets. If they think a student was violating a rule, they'll search him. That was true before the decision, and it's true now."

It may be that the ACLU -- which in the past always tried to make the real world adapt to the Constitution, rather than the other way around -- is becoming more "reasonable," as Ed Meese might put it. But this is the wrong Supreme Court decision for the ACLU to use to accommodate to the standards of "the real world."

New Jersey v. TLO gives the highest court's imprimatur for the first time to a process by which public school students can suffer criminal penalties, including prison, on the basis of searches inside a school that would be illegal if the student were searched anywhere else.

The core of the decision has been most clearly summarized in The Los Angeles Daily Journal, an uncommonly lucid and lively newspaper of legal affairs. Said the Journal: "The court's sweeping ruling could make it virtually impossible in most cases for students to challenge evidence discovered during a school search and then turned over to law enforcement authorities."

For instance, a teacher, now officially told by the Supreme Court that he can search a student without "probable cause," finds evidence that could not be admitted in court if an adult had been searched. The teacher can now hand this evidence over to a cop, who will be allowed to introduce it in court because the evidence was lawfully obtained by the teacher under the special lower standard for students authorized by the Supreme Court.

This will also enable undercover cops working the schools in New York and other places to collar youngsters on the basis of a school official's search, which the cops themselves cannot make because they are held to "probable cause" standards inside as well as outside a school.

As Justice John Paul Stevens has noted, "The school room is the first opportunity most citizens have to experience the power of government. . . . (T)he values they learn there they take with them in life. One of our most cherished ideals is the one contained in the Fourth Amendment: that the government may not intrude on the personal privacy of its citizens without a warrant or compelling circumstance. The court's decision today is a curious moral for the nation's youth."