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Dozens of children brought their pets to school for the day, where they took part in competitions like lamb drinking, fancy dress and young farmers.
Talia said it was her favourite day of school because she could bring her lamb Louis to meet her friends.
"It's very fun - and everyone puts different costumes on their lamb. It's so funny.''
She used clothes that she wore when she was a baby to dress Louis.
Principal Kay Teviotdale said the day was a celebration of the Thornbury community.
"Its a celebration of rural. Everything rural. We had kids doing crafts, bringing along the animals, talking to the judges about the care of the animals. It's a great and fun experience.''