They hid their small charges, remained calm, and quietly led them outside - instructing them to close their eyes so they would be shielded from the carnage.

One of the most damning aspects of this tragedy is that the teachers knew immediately what was unfolding: another school shooting.

They also knew that, if found, they'd be executed without mercy, as would the children in their care.

A parent, Brenda Lebinski, said her eight-year-old daughter had been among children saved by a teacher who locked them in a closet. ''My daughter's teacher is a hero,'' she said. ''Everyone was in hysterics - parents, students. There were kids coming out of the school bloodied. I don't know if they were shot, but they were bloodied.''

Hampered by a gunshot wound in the leg, the vice-principal Anthony Salvatore crawled back inside the school office, frantically urging colleagues to phone 911.

Another quick-thinking member of staff was Kaitlin Roig whose ''happy'' morning meeting with her 14 students was suddenly interrupted by the unmistakable sound of rapid gunfire.

Ms Roig, 29, said she leapt up, closed her classroom door and then ushered the children, aged six and seven, into the adjacent bathroom. It was so tight some of the pupils had to be balanced on top of the toilet so they could all squeeze in. She then jammed a wheeled storage unit in front of the door and hoped for the best. ''We all got in there. I locked us in,'' she told America's ABC Network. ''I don't know if [the gunman] came in the room … I just told them we have to be absolutely quiet.

''If they started crying, I would take their face and tell them, 'It's going to be OK,''' Ms Roig said. ''I wanted that to be the last thing they heard, not the gunfire in the hall.''

While staying strong for her pupils, Ms Roig was convinced they were ''all going to die''.

Speaking through floods of tears, she said: ''I told the kids I love them and I was so happy they were my students … I said anyone who believed in the power of the prayer, we need to pray and those who don't believe in prayer, think happy thoughts.''

She paid tribute to the children who had remained relatively calm throughout. ''They asked, 'Can we go see if anyone is out there … I just want Christmas … I don't want to die, I just want to have Christmas.'''

Third grade music teacher Maryrose Kristopik saved 15 children by hiding them in a closet while the gunman Adam Lanza loomed outside, screaming: ''Let me in! Let me in!''

The Daily Mail in Britain reported Ms Kristopik had been hailed a ''hero'' by parents after herding the children to safety in the closet and barricading the door. An unnamed mother, whose nine-year-old son was among the children, said: ''I want to thank her. She saved their lives.''

In the library, Yvonne Cech, a librarian, locked herself, an assistant and 18 fourth graders in a closet behind filing cabinets while the sound of gunfire thundered outside.

Diane Day, a school therapist, hailed the school's unnamed ''lead teacher'' as ''our hero'' after she was shot twice while barricading a lockless door with her body to keep Lanza out of a classroom occupied by staff who had been in a meeting before the shooting.

Ms Day told The Wall Street Journal that, after the school principal, Dawn Hochsprung, and school psychologist Mary Sherlach had run out of the room to see what was happening, the shooter arrived and tried to force entry. Lanza was thwarted by the teacher who was wounded in the leg and arm as he opened fire through the door.

Ms Hochsprung and Ms Sherlach did not return and were later confirmed dead.

The Stamford Advocate reports the brave principal had, crucially, managed to activate the school's public address system before she was killed. In alerting the rest of her school that a killer was on the rampage, the principal's last courageous act almost certainly prevented further bloodshed.

One parent, Stephen Delgiudice, did not know who had made it to the button attached to the address system but confirmed it had alerted pupils and teachers to the intruder, playing a critical role in saving his own daughter's life.

''My daughter said she heard cursing come over the loudspeaker and that cursing wasn't the right thing; so the teacher, Mrs Martin, looked at the kids and she said 'Get in the corner.'

''She did a very good job. She locked the door and that basically saved their lives, I think.''