LEXINGTON, Va. — Without warning, a drum roll explodes in the darkness after midnight, echoing through the still barracks, jolting the cadets of the Virginia Military Institute out of their sleep. It is ominous and relentless, as urgent as it is foreboding.

At every door of the four-story complex, there is a heavy knock, an order to fall out and, above the drumming, a shouted, repeated announcement: "Your Honor Court has met . . . Your Honor Court has met." In every room, the lights snap on.

Within minutes, dressed in robes and pajamas, chins tucked, chests out, all 1,200 young men of the VMI Corps of Cadets stand at attention in ranks around a dim inner courtyard, assembled for the excruciatingly painful ritual of a "drumming out." One of their own has cheated. Hehas been banished for breaking their sacred Code of Honor.

Resplendent in dress uniforms, members of the Honor Court march through an arch into the yard. The court president announces the name of a cadet found guilty of violating the code and intones: "He has placed personal gain above personal honor. He has left the institute, never to return. His name is never to be mentioned again."

It is a moment none of them will forget. After 30 years, Lt. Col. Mike Strickler, a VMI graduate now on the institute's staff, vividly remembers the spring morning when a classmate was drummed out for cheating, just 10 days before he was to graduate. During one year while Strickler was a cadet, six members of the regiment were drummed out. In another year, there were only two. He remembers them all.

He also remembers the 12-word code that every VMI "rat" memorizes the day he arrives: "A cadet will neither lie, cheat, steal nor tolerate those who do."

That code, said Danny Felton, one of about 225 fourth classmen due to graduate from the 155-year-old institute this spring, "is the cadet's most cherished possession."

Variations on this rule of conduct are embraced by 100 or so institutions of higher learning, in addition to the Army, Navy and Air Force academies and venerable military schools such as VMI and the Citadel. They range from small private schools such as Washington and Lee and Bryn Mawr to Princeton and Rice, and to the University of Maryland with 38,000 students.

At some, they are enshrined and forgotten in student handbooks; at others, they have become the cornerstone of academic integrity.