An elementary school principal from fire-ravaged Fort McMurray is crediting her staff for ferrying 70 students to safety through the heart of the blaze.

Laura Dennis says the swift growth of the fire Tuesday afternoon left her with little choice but to get the children out of Good Shepherd Catholic School before official evacuation procedures could get underway.

She mobilized her staff, instructing them to take as many students as they could in their own vehicles and head toward another school that wasn't in the direct line of fire.

Dennis says the convoy drove metres from walls of flame that were destroying the neighbourhood of Beacon Hill, leaving her terrified for everyone's safety.

"It was so scary driving along Beacon Hill with all these little kids in cars, and the flames were so close," Dennis said, audibly fighting back tears at the memory.

Fort McMurray wildfire

This photo is from video captured by Michel Chamberland as he drove out of Fort McMurray following a mandatory evacuation because of a wildfire. (Michel Chamberland)

"There were some live embers dropping onto the road, and little things were blowing by the sidewalks and catching fire, and it was truly terrifying."

Dennis says the teachers remained with their students for as long as 10 hours, foregoing the chance to return home for their own belongings, until everyone was safely reunited with their families.

"None of my staff got home. They all had to leave right from the school," Dennis said in a telephone interview from Edmonton where she fled from the fire.

"We put kids first, and lots of them have their own families, so it's quite commendable."

Day began under clear, blue skies

Dennis said no one had any inkling of what the day had in store when students swarmed into class under clear, blue skies on Tuesday morning.

By lunch time, however, the situation had changed. Dennis said she knew trouble was looming based on the rapidly deteriorating air quality and dark clouds of smoke drifting on school grounds.

Dennis ended lunch recess a few minutes early to get the students back inside. Almost immediately thereafter, she said, terrified parents began arriving in droves to take their kids out of harm's way.

About 190 of the 260 students were gone within an hour, leaving staff and about 70 students to wait for instructions on what to do next.

Dennis received word from the town that school buses would collect the stragglers and take them to another Catholic school in a less hazardous area, but soon found the vehicles that were to bring them to safety had been caught up in the melee of people trying to flee the city.

Snap decisions had to be made

Feeling the buses were taking too long, Dennis made the "snap decision" not to wait and to get the children out in staff vehicles instead.

She said it was the only way to ensure everyone's safety and quell the student's anxiety.

Fort McMurray wildfire

A wildfire approaches the city of Fort McMurray on Tuesday May 3. (Terry Reith)

"One little boy was crying and saying, 'I'm scared.' And I said, "yeah, it's ok to be scared, but just know we're going to look after you," she said.

Dennis said the 13 cars in the convoy would have reached their destination in 10 minutes under normal circumstances, but were forced to move at a snail's pace past some harrowing sights.

Most of the cars made it safely to the other school, but Dennis said she and two other staff members were directed off the route due to the volume of traffic and the rapidly escalating blaze.

Each child had to be accounted for

She said she found herself stuck at a hotel speaking to Hughes and other staff members to try to account for each child. Most met up with family members at the second school, but six couldn't connect with their parents.

Dennis said staff members made sure they stayed with those half dozen students until they were safely restored to family. In several cases, this involved coordinating with parents to meet up along the evacuation route.

In one instance, Dennis said a teacher drove a student all the way to Anzac, about an hour out of Fort McMurray, and didn't hand the child over to family members until 12:30 in the morning.

Dennis said she felt powerless being separated from the group at the time of the evacuation, adding she wanted to be alongside her team rather than coordinating the activity from the sidelines.

She deflects all credit for the safe evacuation, saying the dedication of the staff almost certainly prevented a tragedy.

"The first inclination you want to do is go and get your family safe, right? But if we hadn't had the teachers stay, and we didn't have that many cars, we probably would not have gotten those children out safely."

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