As the threat of war loomed large yesterday, hundreds of students and activists marched from Cambridge to Boston expressing raucous opposition to U.S. policy in the Persian Gulf.

Chanting "One, two, three, four, we don't want your bloody war," about 300 protesters, some wearing gas masks and others smeared with fake blood, blocked traffic as they wound their way through city streets.

The demonstration was generally peaceful, but windows were broken at a federal office building in Boston. In the scuffle which followed, one antiwar activist was arrested.

About 80 Cambridge Ringe and Latin School (CRLS) students left school to join the protest. High school and college students made up the majority of the crowd and prompted chants such as "Money for tuition, not for ammunition."

On their way to Boston, the marchers stopped at CRLS, urging the students inside to join them. As the crowd yelled, " Out of school, into the streets," students pressed their faces to the classroom windows. Some protesters confronted CRLS security guards and handed bumper-stickers to youths through an open door.

Rachel B. Weinstein, a junior at Cambridge Rindge and Latin School, said that many students there had stood up and walked out of classes. Most had parental permission, but others faced disciplinary action, she said. "It's important to be here," Weinstein said, "but it's completely different from school."

"I don't think I'll be able to do any more studying, because I'm going to be working for peace. I've got a paper that I'm just going to take an incomplete on," said M. Emmett Rosenthal '91-'92, one of a handful of Harvard students who participated in yesterday's protest.

At the U.S. Armed Forces Recruiting Center at 955 Mass. Ave., the group stopped to throw snowballs, put stickers on the window, and shout, "I want to kill, let me in." The blinds to the recruiting station were closed and the doors were locked. As snowballs whizzed by his head, a frowning Cambridge police officer complained, "This is supposed to be a peaceful demonstration."

When the crowd reached Central Square, it staged a "die-in." In a busy intersection, about 40 marchers dropped to the ground and cried in feigned agony.

As the group continued towards Kendall Square, stunned bystanders lined the streets, and many motorists added their honking horns to the din of the rally. But some drivers challenged the protesters.

"Freedom to Kuwait. I am for war. Peace for Kuwait. Peace for Israel. Kill Saddam Hussein," said immanuel Glazer, 46, a Soviet Jewish emigre driving a truck which was caught in a traffic jam caused by the protest. "I am strictly for Bush's policy," he said.

Bill and Beth Kostopoulos, proprietors of the Kendall Flower Shop, sold "peace ribbons" to the protesters at prices ranging from 50 cents for a small bow to $1.00 for a large one. Bill remarked that the protesters seemed, "nice and peaceful" and said that he didn't think there would be a war.

Leaving Kendall Square, the group crossed the Longfellow Bridge into Boston. After another brief die-in in Leverett Circle, the protesters continued towards Government Center.

At an Exxon service station along the march route, some protesters applied stickers to a sign and embraced a gas pump. An employee swung at the activist with a squeegee, but failed to make contact.

"He's a businessman. He's not for war," a customer yelled at the marchers.