The Ysgol Penmorfa pupils were involved in a four vehicle collision on the westbound carriageway, close to the Shell garage, at 10:15am.

A total of 94 youngsters were travelling back to Prestatyn on two coaches when they were involved in a pileup, leaving a number of them suffering from bruises from their seatbelts, shock and nausea.

A Welsh Ambulance Service spokesperson said: "Control dispatched three emergency ambulances, one rapid response vehicle and four officers to the accident which was declared a major incident due to the number of children needing hospital treatment.

"Twenty children and one adult were treated for minor injuries by ambulance staff at the scene and taken to Ysbyty Gwynedd for further treatment, along with the rest of the children on two replacement coaches accompanied by paramedics and officers."

Four ambulance officers co-ordinated the casulaties at Ysbyty Gwynedd, and the vehicles were recovered.

The ambulance service spokesman added: "The accident was declared a major incident because of the number of children involved, not the severity of this injuries."

Pupil Patrick Farrell, 10, said the impact came as a shock.

His mum, Samantha added: "We've just been to the school and have to say that Mr Wynn will be getting a letter of thanks as he dealt with the situation in the most amazing way."

Sadie Hughes, 10, of South Avenue, Prestatyn, was sitting behind the driver of one of the coaches.

She said:"I was thrown forward and banged my head on the rail. I got thrown back into my seat and all smoke was coming out of the engine and the front window had smashed."

Sadie's mum, Paula added: "We are grateful that everyone is ok. I would like to thank all the staff at the school and say thank you to Bangor hospital for treating everybody so quickly."