Chapter 6 of Adventures of Tom Sawyer

Pretending to be sick? The first paragraph is quite explicit that Tom is looking for a reason.... symptoms to be sick. He doesn't want to ge to school.

Tom lay thinking. Presently it occurred to him that he wished he was sick; then he could stay home from school. Here was a vague possibility. He canvassed his system. No ailment was found, and he investigated again. This time he thought he could detect colicky symptoms, and he began to encourage them with considerable hope.