The children of Norton St Philip Primary School returned to school on Monday to discover a UFO had crash landed in the playground.
The pupils arrived to find a police car with its blue lights flashing, yellow hazard tape surrounding the area, a crime scene tent and two scientists wearing chemical suits and breathing apparatus.
Teacher, Claire Vowell, said the children were able to dress up as crime scene investigators, once they had been given the okay by the forensic scientists.
She said: "The first half hour of the day saw the children stare open-mouthed as scientists measured, recorded, bagged and photographed metal wreckage strewn across their school field.
"Once the scientists had deemed the area safe the children were able to become crime scene investigators."
Year 1 children donned special red protective suits and they set out into the field to join their peers in other classes with magnifying glasses, evidence markers and evidence bags.
About 20 bags of evidence was collected and taken back to the classroom for investigation.
More excitement came in the afternoon when a white van drew up containing another scientist and a member of MI5 complete with black suit, sunglasses and an earpiece.
The children watched as their beloved spaceship was taken away for forensic examination.
Mrs Vowell said: "The school would like to thank JW Ransome and Sons for all their help with the crash scene debris and everybody else involved during the day."