The one with cheating.
Actually, cheating is nothing, till it harms somebody in some way. Single persons life is insignificant to society and if someone had cheated more in one's childhood, I guess it wouldn't have influenced a lot of people. Maybe relatives, friends, and that's all. Cause most of child's cheating, if it were, was only about studying. Cheating for taking one grade higher, for example. Usually you would have got A instead of B, if you had cheated properly, but at the same time cheating might be your expelling.
Children's cheating isn't so harmful, but if being a child you hadn't stopped cheating, then adulthood cheating might be your worth nightmare. There will be nobody to take your responsibilities, because everyone has their own duties, and they simply don't have time to help you. If you are a hard-working kind of person, and you don't have to cheat, than probably, you must have studied well at your school days.
But what about those who are not so clever in ordinary stuff, but still have a high ranking position in society. What is interesting if you want to be on such place, you must be completely different person. Cause knowing how to rule people doesn't oblige you to know math.
Yet mistakes of such people, and what is worth, their purposeful cheating can have way bigger consequences. A factory manager money cheating can impact not only factory's reputation but also workers safety, who can die due to lack of new breathing mask for instance. In general, the more power you have, the more responsibility is behind your decisions. And I hope that phrase “Once a cheater – always a cheater” is not about you, or at least you should think about it.