I realize that might seem counter intuitive, but seriously, that's my reason. First, the only person you really hurt by cheating in school is yourself. Your teachers don't really care and are not hurt by it. Your parents aren't hurt, though they may be disappointed in you. It really does turn out that the only person affected by your cheating is you.
Ok - so why isn't it a good idea to cheat if the only person affected is you? Well, let me tell you a little story. I was a level 1 student in high school. One time I had to make up a test I had missed during the level 3 class. I was shocked. Those kids put more effort into cheating than I put into studying. So, right off the bat, the lazy person inside me was wondering why they were willing to work so hard to cheat, but not willing to work less hard to just, you know, study. Because, the lazy route to good grades, really is studying.
The 2nd thing that struck me was that for all the time and energy they put in, which was again, was significantly more than it would take to just read the friggin book, it didn't actually help them get better grades. Their grades, with the cheating, were still crappy, which is why they were still in level 3.
Rationally, what they were doing doesn't make any sense. They were working harder for bad results. They could have worked less hard and gotten better results just by deciding to learn the material instead of trying to cheat. So, not only did they not learn the material, they worked harder to not learn the material and their grades were still crappy. The mind boggles.
When you think about whether to cheat or not, take the lazy route and just read the darned book.