Presto Change-O by Audrey Wood

Matthew and Jessica learn at last the value of co-operation, but only after turning mother into a frog .... Matthew and Jessica's competitiveness gets them in to trouble when a magic trick goes disasterously wrong. They realise that they can only undo the spell by working together. This fun story teaches the value of co-operation and explores the issue of sibling rivalry.
Binding: Paperback / softback