Everything seems so simple as a child. Anything you say, goes. Kids believe whatever lies or truths you feed them. So, when you tell them that their mom is going on vacation so they have to stay with you for a while, that's what they believe you.
Class 1-A and class 1-B are going on a field trip to a soccer camp for two weeks. You are really good at soccer and are hyped to go. And at the end of the two weeks, both classes will face each other in a match with the winning class not having to do any work for the next two weeks.