Everything you need to understand or teach Lassie Come-Home by Eric Knight.
A Yorkshire, England, family is forced to sell their beloved collie, Lassie, to pay their bills during a time of economic crisis and unemployment. The son is especially devastated to lose his companion who devotedly met him each afternoon when he came home from school. Lassie's new owner, a wealthy duke, takes her to Scotland. However, she escapes and travels approximately one thousand miles south to return home.
Her journey requires her to traverse challenging natural obstacles such as rivers and snow drifts. Lassie encounters both helpful and harmful humans and animals and suffers injuries. Her determination, perseverance, and loyalty results in a reunion which foreshadows better times for Lassie and her chosen masters.