Dozens of students were assembled in the synagogue of their high school for morning prayers Tuesday when they heard a massive boom. 

The teenagers knew immediately what had happened. Shouting "bombing, bombing," they rushed to the gate of the Ort Spanian High School. 

On the street outside, they saw the smoldering wreckage of a bus torn apart by a Palestinian suicide bomber. Nineteen Israelis, including at least one student from Ort, were killed in the attack, and several youngsters were among the wounded. 

Shmuel Calfon, 15, was in the school synagogue when he heard the blast and said he ran with the others to the gate. "Everyone was on the [cell] phones at once" to call home and assure their parents they were safe, Calfon said. "It's awful. It's impossible to imagine." 

Another student, 17-year-old Eliran Ben-David, said he was not rattled by the attack, noting that he witnessed a December bombing in downtown Jerusalem that killed 10 people, most of them teenagers. 

"I've seen so many attacks, I didn't get excited," said Ben-David, sitting under an olive tree near the school gate with a group of friends. 

Ben-David and his friends said they intended to spend the rest of the day watching soccer on TV rather than going to school. "When you have friends who are missing, maybe hurt, you just don't feel like it," he said. 

District supervisor Ruth Meir said the outward bravado masked inner turmoil, fed by students' constant fear of attacks in Jerusalem, which has been hit hardest in the current wave of shootings and bombings by Palestinian extremists. 

Education Minister Limor Livnat said Israel must take harsh action. "How can we go on when our children are taking buses on their way to school and find themselves in the middle of a terror attack?" Livnat said during a tour of the Ort Spanian school. "We cannot fool ourselves. No normal country can go on like this, with any more terror attacks." 

Since the outbreak of fighting in September 2000, Palestinians have carried out 70 suicide bomb attacks against Israelis. In all, more than 540 people have been killed on the Israeli side and more than 1,700 on the Palestinian side. 

Tuesday's blast gutted the bus and peppered nearby vehicles with nails, packed inside the bomb to increase its lethalness. 

School secretary Dina Atzmon said although most students were already in school when the blast occurred, just before 8 a.m., there were always stragglers. Many of the school's 600 pupils come from the nearby southern Jerusalem neighborhood of Gilo and travel on the No. 32 bus route, on which the blast occurred. Atzmon's son was one of the late-comers, but he escaped the blast. 

Michael Lasri, 15, ended up on the No. 32 bus because he had woken up late and spent too much time fussing with his hair, said his mother, Devorah Lasri. 

The teenager, who suffered cuts and bruises, said he saw the bomber board the bus. "He was a little bit fat, wearing a red shirt. I saw him for only a few seconds, from the moment he got on the bus until the moment he blew himself up," Lasri said from his hospital bed. 

In the hallways of the school, students talked quietly among themselves and a mother and son hugged, while the boy sucked on a popsicle. 

In Atzmon's office, the phone rang constantly, with parents frantically seeking reassurance that their children were safe. Teacher Eliahu Tsur fielded the calls, while Atzmon checked names from the school roll. 

"There's a lot of hysteria," Tsur said. "We're trying to calm the parents and stay calm ourselves."