The Tumbling Mice by Susan & Wendy Mitchell

Sophie loves gymnastics, even though somersaults are very tricky. No matter how many times she tries to do one, she cannot quite get it right. Sitting in the garden one day, wondering if she will ever be able to do a somersault, Sophie is very surprised when three little mice peep out from their hiding places to show her exactly how it is done. The strange thing is this special, natural sort of magic just seems to vanish – poof! – the moment a grown-up lays eyes on it…