...or what can happen if you let kids follow their curiosity. A simple lesson on triangular numbers caused much interest - two boys started doing each triangle individually (3, 6, 10 etc) then decided doing one big triangle would answer all their questions. They are only 9 years old, but I'm hoping the next step is that they look for a formula. The lesson only needed them to go to 10 to answer some logic questions, but they were so into it I let them carry on. "Can we stay in and finish it, Miss?"