“It wasn’t too long after creation that the animals got together to form a school. They wanted the best school possible–one that offered their students a well-rounded curriculum of swimming, running, climbing, and flying. In order to graduate, all the animals had to take all the courses
The duck was excellent at swimming. In fact, he was better than his instructor. But he was only making passing grades at climbing and was getting a very poor grade in running. The duck was so slow in running that he had to stay after school every day to practice. Even with that, there was little improvement. His webbed feet got badly worn from running, and with such worn feet, he was then only able to get an average grade in swimming. Average was quite acceptable to everyone else, so no one worried much about it–except the duck.