The Vicar, Mr. Blomefield, has many children, and they sometimes come to play with Miss Jessie and Miss Flora. When they come to visit, Merrylegs is always busy, for the children love to get on his back and ride him around the paddock for hours. One afternoon Merrylegs is out with them a long time. When James brings him back to his stall, he is scolding the horse, warning him to behave better next time.
Black Beauty asks what he did to cause trouble. Merrylegs says he taught "those young people" a lesson about what was too long a ride by pitching them off his back when he had had enough. Black Beauty is shocked at such behavior and asks if he threw off Miss Jessie or Miss Flora. Merrylegs is indignant, saying he would never treat ladies or "little ones" in such a way. He is their instructor, understanding their need for him to go slowly until they are more stable and confident; he claims he is the “best riding master” the children can have.
It is the boys who must be taught a lesson. They, like colts, must be broken in and “taught what’s what.” The younger children had ridden Merrylegs for several hours, and the boys wanted a turn. He was agreeable and galloped them around the fields and orchard for an hour. They had fashioned a riding whip from a hazel branch and whipped the horse a bit harder than he would have liked, but he good-naturedly continued their rides. Once Merrylegs thought enough was enough, though, he stopped several times. He hoped they would take the hint that the ride was over, but boys think horses are like machines, without feelings, and can keep going inexhaustibly.
When the one who was whipping him failed to take the hint, Merrylegs rose up on his hind legs and deposited the boy gently on the ground. The boy remounted, and the horse repeated his action. Merrylegs simply wanted to teach them a lesson, but the boys complained to James. James was angry at the size of the sticks the boys had used as whips, and Ginger says she would have given the boys a good kick which would have taught them a lesson. Merrylegs says he would never abuse the trust placed in him by the master or make James afraid of him.
Merrylegs is aware of his role as protector of the children. He has even heard the Squire tell Mrs. Blomefield that she could trust the horse, and he would never sell Merrylegs because of that. It would be ungrateful of the gray horse to betray that trust because of a few ignorant boys who treated him badly. He loves his masters and is afraid he would end up worked to death by harsh taskmasters who only cared about how much he could carry or how fast he could go. He has seen such behavior before and hopes he shall never find himself in that position.