A 12-year-old girl is in hospital in critical condition after she collapsed at St. Gregory School in Nepean this morning, but paramedics are praising school staff members for their efforts in saving her life.

Paramedics and firefighters responded to the Catholic elementary school at 148 Meadowlands Dr. just after 9 a.m. after the girl collapsed in a hallway.

Children were coming into school from the cold when the grade six student stopped breathing and crumpled to the floor.

One staff member called 911 immediately while an education assistant who just finished a first aid training course began administering CPR.

Paramedics and firefighters helped revive a 12-year-old girl who collapsed at St. Gregory School in Ottawa Tuesday. (CBC)

Paramedics arrived five minutes later and assessed the girl before firefighters continued CPR.

Paramedics delivered one shock from a defibrillator, found a pulse and inserted a breathing tube.The girl was struggling to breathe on her own and she began to move. She is listed in critical condition at hospital.

School principal Paul McGuire credits his staff with taking control of the situation until medical professionals arrived.

"I've not been in a situation where we've had to call on those skills before, but I'm very glad that we have them," said McGuire. "We have several people who are trained with CPR and I'm very thankful that we have that kind of training here."

It is not yet known what caused the girl to stop breathing, but paramedics believe the quick actions of school staff helped her regain a pulse.