Accompanied by a convoy of 12 teachers and chaperones, 102 students from the Jackie Robinson Middle School in New Haven, Conn., set out early last Tuesday on the annual school bus trip to Washington, excitedly expecting to see the monuments they had read about and studied all year.

But their story-book excursion changed to a sickening experience Thursday morning, when a fifth-grader, a teacher and two bystanders were stabbed with an ice pick by a man in the cafeteria of the Hotel Harrington downtown.

Yesterday, two buses and a van pulled up to the Washington Hospital Center and the homeward-bound contingent waved fondly at one of its most admired teachers, Willie Freeman, who was seated in a wheelchair at a third-floor window to see them off.

But the students' excitement and optimism was hushed again as they drove out of the city. They had been unable to see their injured schoolmate and friend, 10-year-old Kevin Staton, who was still under sedation at Children's Hospital, listed in fair condition with a stab wound to the abdomen and a punctured spleen.

Students, teachers and New Haven public school administrators declined yesterday to blame the District of Columbia for the violence that marred the four-day outing.

"I'll be back next year, more so than ever," Freeman said, lying in his hospital bed and holding his right hand over the wound in his abdomen.

Ten years ago, he helped organize his school's first trip, and until Tuesday, he recalled, there had been no serious problems, no bad experiences.

"We're all committed to bringing the children here. The trip is an extension of the classroom where they can learn responsibility," he said, "learn how to depend on each other and learn about the real world.

"Unfortunately, we live in that real world, and things like this happen. Still, it's a learning experience. This man the assailant is a perfect example of what people shouldn't do."

Gerald Tirozzi, superintendent of the New Haven school system, said yesterday, "I don't think that what took place is a reflection on Washington D.C.

"What happened to the kid and the teacher could have happened anywhere . . . It could happen in a grocery store, in a Midwestern town or in a hotel lobby in Washington, D.C."

Most of those on the trip were in the hotel cafeteria Thursday shortly before 7:30 a.m when the stabbing occurred. They were looking forward to boarding the bus again to meet their congressman on the steps of the Capitol.

Kevin Staton had just stood up from the table to return his tray, Freeman recalled yesterday, when a man with his hand concealed in a brown bag passed by and punched the boy in the stomach. As it turned out, the assailant was holding an ice pick in the bag, police said.

The child screamed and buckled over the table in pain, Freeman recalled. At that point, Freeman got up and ran over to the man, who then turned toward the teacher, ready to attack again.

"The guy opened his arms like he was going to come after me, which he did," said Freeman, who has had some training in martial arts. "Luckily, I could kick him in the chest." But the short lean man came at him again, this time jabbing Freeman in the right side.

"I did not know he'd stabbed me," the teacher recalled. "I felt this sharp pain in my right side, then he ran out the door."

Freeman, built like a halfback, held his side and ran after the assailant, weaving through the morning rush-hour crowd on E Street NW. Several people joined in the chase, he said, including a member of the Uniformed Division of the U.S. Secret Service who happened to be in the area.

They cornered the man behind the hotel, handcuffed him and took him back to the hotel to be identified. Police said later that the suspect was Chawe Hymm Thom, 47, of no known address. He has been charged with assault with intent to kill in connection with the stabbings.

Richard Gray, 50 of Howard Road SE, had tried to restrain the man inside the cafeteria and was also stabbed, but released after treatment at Washington Hospital Center. A fourth person reportedly fled after being stabbed in the incident, police said.

Bettie Staton, who flew here Thursday, said yesterday that she is thankful that her son survived. "He's getting fair and complete treatment here at Children's ," she said. "It's very unfortunate what happened. I just thank God that it's not as bad as it could've been and just grateful that he is alive."