One McKinley High School teacher was punched in the nose, another hit on the side of the head, a third pushed in the face, and an administration official struck in the back with a snowball Thursday afternoon by a roving gang of youths, D.C. police and school officials said.

After the gang invaded the school and ran around kicking classroom doors, a McKinley student, Kenneth McCrory, suffered lacerations of the right arm in a fight with a group of youths outside the school, according to McKinley principal Athel Liggins. McCrory was taken to Howard University Hospital by ambulance, treated and released.

Thursday's incidents point to a dilemma that school officials, teachers and students say is growing worse -- how to keep nonstudents from disrupting classes.

Liggins and teachers are critical of a ruling by school officials last year that most of McKinley's 53 exit doors must be unlocked during school hours. That ruling has made it difficult, teachers say, for the school to control who enters and exits. The city's fire code regulations stipulate that fire exits must be kept open, regardless of security problems.

"Most of our discipline problems are from outsiders, people who don't belong here," Liggins said. "We had no discipline problems hardly at all when we had our security program of locked doors and identification cards."

"Now, anybody who wants can come in; kids have been assaulted, lockers have been broken into," he said. "We've had all kinds of problems since they have taken the means of controlling the building away from principals."

Most of Thursday's incidents occurred on the second floor of the school, at Second and T streets NE, Liggins said. No one was arrested in the incidents.

One of those assaulted, Jorge Hernandez, a Spanish teacher at the school for five years, said he had been working in a second-floor office between classes when he heard a loud banging noise.

"It was during the seventh period. about 2:20 or 2:30 p.m., and I heard the noise. I came out, saw them banging on classroom doors, kicking them, and I heard one of them say I'm going to hit this one," Hernandez said.

"One of them, a youngster about 16, hit me in the nose with his fist," he said. "It really hurt and it bled a lot."

"We've had problems before of students and others walking around in the halls during class periods, calling to their friends inside classrooms, laughing and talking loud, but it's the first time they have done this," Hernandez said.

"Discipline is bad and it keeps us from transferring knowledge to students," Hernandez said, pausing and listening to loud laughter and noise outside his classroom. "Did you hear that? That happens all the time. That's what they do."

Seconds later, assistant principal Joseph Brown blew a whistle to interrupt a group of loud-talking students in the hall. "I don't want you up here anymore," he shouted to them.

Michael Baylinson, a laboratory techniques teacher, said, "In the three years I've been here things have gotten worse. We've had beer drinking, pot smoking and crap games in the stairwells. I've talked to several people standing in the stairwells doing those things, and they just ignore me."