THE principal of Holy Cross Boys' PS in north Belfast has said he feels lucky that no one was killed by an improvised weapon left in a drain in the school.
Kevin McArevey discovered the device when he was helping the caretaker clear sewers on Monday.
Police confirmed the gun had the potential to fire a high capacity round.
The school, which has 410 pupils and around 50 members of staff, is due to reopen today.
It had been closed yesterday while police carried out a thorough search of the grounds, which included lifting all the manhole covers.
Mr McArevey said: "None of us wants to be dragged into the past. We want to help our children learn and develop for the new digital age.
"It's about bringing positivity to the area. We don't need this negativity at all."
The principal praised his "quick-thinking staff" for the way in which they handled the evacuation, managing to get all the children onto the pitch within two minutes.
He added: "We are lucky. There could have been loss of life and there could have been damage to the school. Someone was looking down on us."
Police said the weapon was most likely to have been left in the school by dissident republican terrorists and was probably intended to kill or seriously injure police officers.
In April 2017, dissidents republican were blamed for dumping a bomb outside the school.
The device, contained in a metal cannister, was defused.
It was claimed the bomb was abandoned after those transporting it - believed to be members of the New IRA - suspected they were under surveillance and fled.
Police confirmed the school would reopen today.
Chief Superintendent Jonathan Roberts said: "I would like to thank the local community for their patience and understanding since this began. This disruption was necessary in order to ensure there was no further risk to the children in the immediate area.
“Detectives from the PSNI’s Terrorism Investigation Unit have now commenced an investigating and are appealing for anyone with any information that can assist with their investigation or anyone who may have noticed any suspicious activity in the area recently to contact detectives on 101 quoting reference 1169 23/09/19. Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111."
