Students who took the Law School Admission Test in Memorial Hall last Saturday will have to retake the test in May because of a "breach in security," a spokesman for Education Testing Services said yesterday.

Head proctor Leonard Holmberg, registrar of the Summer School, interrupted the approximately 250 students taking the test because of an outside disturbance caused by the bicentennial parade on nearby Broadway. Holmberg allowed those taking the test to leave the room for more than a half-hour, in violation of testing service rules.

Robert G. Wiltsey, head of the LSAT division at ETS said yesterday the test would have been valid had Holmberg required the test takers to remain in their seats while the test was halted for 35 minutes.

"The likelihood of people talking about the test during the break forced us to invalidate it," Wiltsey said.

Holmberg yesterday defended his decision to allow students to leave the room, claiming that ETS approved of his procedure when he called them after the test.

Wiltsey said the test would be re-administered on either May 3 or May 10.

Russell Simpson, dean of admissions at the Law School, said yesterday that a mark showing invalidation of this test by ETS would appear on each student's college transcript, but that it would not affect a candidate's chances for admission to law school.

Simpson said invalidation of test results due to unavoidable interruptions during the exam happens to at least one testing center each time the test is administered. "It's always a reason for which students can't be held responsible," Simpson said. "We ignore that mark."

Students were asked to close their test booklets 13 minutes after the start of Section II, a 40-minute test.