Etched into one of the desks in Robert Washek's classroom at Sherwood High School in Montgomery County is a curious carving: "DMZ=demilitarized zone." It's a crib amid the profanities and declarations of love, a guarantee of at least one correct answer when Washek tests his 10th grade contemporary issues class on the details of the Vietnam war.

It is also testimony that to this generation of students, the echoes from Vietnam are as distant and faint as those from Appomattox, the Argonne or El Alamein.

Washek was drafted in 1969 and spent more than a year with the Army stationed 30 miles outside Saigon. Today, trim but graying, he teaches history to students whose lives are largely untouched by the war he helped fight.

Lecturing on the origins of the war recently, he talked about containment, the domino theory and how successive American presidents increased U.S. commitments in Southeast Asia. When Washek had finished, his students began to respond in equal measures of adolescent innocence and disdain:

"Why'd we go in the first place?"

"I wish Goldwater could've gotten his shot."

"We should've just blown 'em up."

"We could have won."

Even as the Vietnam war becomes a subject of history, taught to high school students and studied by scholars, the debate over its purpose, conduct and ultimate meaning continues. Unlike World War II, which provided clear enemies, a common purpose and, to a great extent, a relatively unambiguous interpretation, the process of learning and writing the history of Vietnam is almost as troubled and complex as the war itself.

A decade has provided students and historians with some of the perspective necessary to evaluate what went wrong at home and in Vietnam, but there is little consensus. As a result, study of the war is uniquely vulnerable to ongoing revision: from conservatives, including Richard Nixon and Ronald Reagan, who are trying to rebuild the case for fighting; to some antiwar activists who are evaluating the strength of their arguments; to military scholars evaluating the strategy and morality of an unwinnable conflict. Interest in Vietnam Grows

Despite predictions that it was a war most Americans would want to forget, interest in Vietnam, on all levels, has grown tremendously, "almost geometrically," in recent years, according to Cornell professor Walter LaFeber. Allan Goodman, an associate dean at Georgetown University, recently conducted a survey that found 30 courses on Vietnam being taught at the top 100 colleges across the nation, with 22 of those courses developed since 1980.

Many colleges lacking separate courses on Vietnam have begun to teach it in some detail in contemporary history and foreign policy programs. Although high school survey courses often run short of time to study subjects as contemporary as Vietnam, teachers, many of whom experienced the war as soldiers or protesters, are making a special effort to include it in the curriculum.

"There are more serious courses on Vietnam today than when it was the top issue in U.S. foreign policy," Goodman said. "I expected Vietnam to drop off the radar screen . . . and I expected it to stay off."

Sandra C. Taylor, who has taught a class on Vietnam at the University of Utah for the last five years, said that during and immediately after the war, there were few courses because "nobody wanted to talk about it at all. Everybody was polarized. Everybody felt they knew everything they wanted to know."

But she said academic interest in the war has now become a "growth industry." Nearly 150 students signed up for her course this spring, three times as many students as the class was slated to hold. Many universities that once offered small seminars on Vietnam have now formed larger lecture courses to accommodate the rising interest.

College classes on Vietnam are now filled with students who have only a slight, "television memory" of the war. Learning about Vietnam, suggested Tufts University professor Martin Sherwin, "is a way of learning about what still goes through the minds of people older than the students. They know they have to understand Vietnam to understand their elders."

One of those elders is President Reagan, who has tried to erase the "post-Vietnam syndrome" by referring to the war as a "noble cause" undermined by a lack of popular and military will. His analysis of the war, one strikingly similar to Barry Goldwater's in 1964, is now being endorsed by conservatives young and old.

Asked yesterday at a White House luncheon about the lessons of Vietnam, Reagan responded that in his view "the great tragedy -- that was the great disgrace, to me, of Vietnam -- $ that they were fed into this meat grinder, and yet, no one had any intention of allowing victory.

"Well, the truth of the matter is, we did have victory. And, incidentally, could I just say, one complaint that I have -- we continue to talk about losing that war. We didn't lose that war. We won virtually every engagement. The Tet offensive was distorted back here in the reporting. That was a victory for our side."

Reagan added that he thought it was Congress' refusal to continue providing aid to South Vietnam after the offensive from North Vietnam that was at fault. "We didn't lose the war," he said. "When the war was all over and we'd come home, that's when the war was lost."

Reagan's interpretation of history -- similar to one advanced by former president Nixon in his latest book "No More Vietnams" -- has been criticized by scholars.

"Reagan would like us to go back to the post-World War II era, but Vietnam won't go away until it's replaced by some other cataclysmic event," Sherwin said. "Vietnam was a cultural earthquake that left the landscape damaged and changed. America looks different than it did. Reagan is trying to reconstruct the landscape as it used to exist. He knows Americans don't like scarred landscapes."

Many students seem to share Reagan's view of the war. Washek said of his own class, "The kids definitely don't like to hear about losing. We fought for 10 years and won every battle and lost the war. That sort of stuns them."

Like Washek, many history teachers say they are confronting a generation that is less self-doubting and more conservative than their own -- in short, a generation largely supportive of Reagan. The same students who questioned the assumptions of their teachers 20 years ago are now finding the tables turned. Typical Attitude: Enlist ---

In a class on Vietnam taught at Prince George's Community College, a typical attitude is that of 20-year-old Paulo Freyesleben, who says he would enlist if the Vietnam War were being fought today.

"You have to work inside the system," he said. "If called up, I'd be among the first to go."

George Herring, a University of Kentucky professor, said he saw the ideological change in his students "about five or six years ago." Herring, author of "America's Longest War: The United States in Vietnam, 1950-1975," one of the most popular texts on Vietnam used in college classes, has taught courses on Vietnam for 12 years. He said his students now are less willing to criticize government policy and intention and are "very turned off" by a book like Frances FitzGerald's "Fire in the Lake," a highly critical study of American policy in Vietnam.

"Among the younger students," Herring said, "there's a general sense that if we were in Vietnam, there must have been a good reason for it."

Yet if the students are more conservative, they don't necessarily endorse Reagan's view of diplomatic and military history or believe in military intervention.

A recent Washinton Post/ABC News poll found that 65 percent of 18- to 30-year-olds believe the country should not have become involved in Vietnam, compared with 28 percent in that age group who still support U.S. involvement. That breakdown mirrors the response of all age groups in the poll.

Nancy Weiss, a Princeton history professor, said students are no longer as animated as they once were about Vietnam, but "I don't see the trend toward conservatism embracing a rehabilitation of the Vietnam experience.

"For all the muscle-flexing and feeling that the action in Grenada was something we had to do, I haven't heard it going hand-in-hand with Vietnam, that it was a good cause and we would have won if we'd only nuked 'em."

Jim Willems, a senior at Woodson High School in Fairfax County, put it another way: "After taking an [American history] class, I feel it was justified to go in there. But once they really got in where people were just dying that much, it didn't seem like there was any objective." Consensus Elusive

For scholars, consensus on the war is as elusive as it is in the classroom.

During the war the best-selling books on Vietnam were FitzGerald's "Fire in the Lake," and David Halberstam's "The Best and the Brightest," an account of how the Kennedy and Johnson administrations deepened their involvement in the "quagmire" of the war. Both books were critical of American policy in Southeast Asia. Ten years later the best-selling account, outstripping both FitzGerald and Halberstam, is a more dispassionate account, Stanley Karnow's "Vietnam: A History."

Karnow's book has sold 200,000 copies in hard-cover and 150,000 in a paperback edition published last fall. He wrote the book as a "companion" to a 13-part series broadcast by the Public Broadcasting Service in late 1983, "Vietnam: A Television History." Many of the new courses in Vietnam history have used the book and the PBS programs as an overview of the issue.

"The animosities and the passions have been replaced by a quest to find out what went wrong and to avoid future disasters," Karnow said. "Pragmatism. That's the word for these kids who are learning about the war now."

Revisionism is another word, however, for the often painful process some scholars and journalists are engaged in when they reconsider their assumptions and work about Vietnam.

FitzGerald said she stands by the substance of "Fire in the Lake," but noted, "There's obviously a feeling that the North Vietnamese were not as wonderful as they hoped they'd be. The boat people, the human rights violations in the country, that changed some people's minds about Vietnam. It's a miserable country, and people want to leave it."

The revisionists are many and of differing positions:

* Col. Harry Summers Jr. of the War College in Carlisle, Pa., and retired general Bruce Palmer are among the military historians who argue that the United States lacked a coherent military strategy in a war that they believe could have been won.

Summers says the Army mistakenly waged an "external" war, seeking a democratic, unified Vietnam rather than fighting to maintain a north-south partition as it did in Korea.

"It's just another area where lack of solid scholarship, in this case military history, badly hurt us," Summers said.

"With the advent of the nuclear age we somehow thought that everything we had learned militarily in the past was irrelevant, that it could be erased."

The military lessons of Vietnam, Summers said, have helped produce more "realistic thinking" about intervention in other areas of the world, including Central America. "Public support is obviously critical for any action in the future," he said.

* In Larry Berman's book, "Planning a Tragedy: The Americanization of the War in Vietnam," Lyndon Johnson is portrayed far more sympathetically than he was in Halberstam's work.

Berman argues that Johnson escalated American troop deployments only at a rate that he thought necessary to encourage conservative legislators to vote for his Great Society programs.

* John Mueller, in "War, Presidents and Public Opinion" describes the antiwar movement in different terms than it is, perhaps, remembered by many people today. Mueller contends that until the Tet offensive in 1968, the Vietnam War was no more unpopular than the Korean War. He also writes that Johnson stopped the bombing of North Vietnam and cut troop escalation in 1968 because of the bleak assessment of the military situation and not because of antiwar protests.

Mueller and Stanley Karnow both endorse the view that the antiwar movement was split between "doves" who opposed the war in Vietnam on moral grounds and "hawks" who opposed it because of the lack of actual success. The antiwar "hawks," Mueller and Karnow say, outnumbered the "doves."

* In "Why We Were in Vietnam," Norman Podhoretz tries to debunk the "moral" arguments against the war. His book, like Guenter Lewy's more scholarly account, "America in Vietnam," blames the antiwar movement and the major press outlets for a naivete' about the communists.

Podhoretz and other conservative critics score some familiar points on the rhetoric of the New Left, but some antiwar activists feel the movement was not always represented by its most reasoned voices. Two antiwar intellectuals, Irving Howe and Michael Walzer, wrote recently that they "were in the difficult position of urging a relatively complex argument at a moment when most Americans, pro- and antiwar, wanted blinding simplicities."

Although numerous books were published during the war and since, there are still limits on archival information available to journalists and scholars. State Department records are open only through 1950, and in Suitland, a huge warehouse holds thousands of cubic feet of uncatalogued documents shipped home from Vietnam by the military.

As more material becomes available, scholars expect the number of serious studies of the war, and the new interpretations that will come with them, to increase. Today's conventional wisdom on Vietnam is likely to be out of date.

Most high school students, however, will continue to get their information from a few pages in a "survey" textbook that represent the residue of countless scholarly accounts.

In "America Revised," a study of American history textbooks, FitzGerald wrote that Vietnam was "a nightmare for editors" who have "to find a compromise formula that would not offend anyone when there was no compromise position and no way to avoid the entire subject."

She noted that history texts for high school students published in the late 1960s and early 1970s had little understanding of Vietnamese history or culture and neglected to mention major points of controversy: the Pentagon Papers, the My Lai Massacre or the Tet Offensive.

Three years ago, education professors Dan Fleming and Ronald Nurse reported on their own study of textbooks and Vietnam and pointed to genuine progress on the subject.

They noted significant revisions in a study of 10 major textbooks and wrote that while FitzGerald's conclusions "continue to have considerable validity . . . the more recent textbooks are more objective and more accurate, and they show a marked dimunition in the degree of nationalistic bias."

Whatever textbook is used, methods of teaching about Vietnam are often more unorthodox, more random and, at times, more compelling and emotional than the usual classroom approach, according to school officials. Because so many teachers were touched deeply by the war, as participants, supporters or protesters, they sometimes bring to their classes the element of testimony.

Mike Carroll is a Vietnam veteran who teaches a contemporary issues course at Bethesda-Chevy Chase High School. Recently he brought to class his 17-year-old slides from his stint in Vietnam.

"There I am, 129 pounds and 21 years old," Carroll told his class. And there he was, wide-eyed and lanky, dressed in fatigue pants and combat boots, his right foot perched on some rubble, a bomb crater in the background. The students were wide-eyed, too. Did he lose any friends? Did he attack villages? Was he scared?

Carroll answered honestly but with jokes and deflections. But just before the bell rang and the lights went on, he became serious.

"Don't forget the lesson," he said. "What I'd say to you is, 'Don't forget about Vietnam and what it was.' Because, who's going the next time? Not me, I'm too old now. Not me. It's you."