There's NEVER a good reason to help a child cheat on a test! Children need to learn to take responsibility for their education. I believe parents should make this a conscious effort from the very beginning to show their kids how important getting an education can be. Make learning fun, so kids will actually try. Everything in life has consequences... By helping a child cheat to pass a test, you're not teaching them anything (except for maybe that cheating is ok... and you see what kind of trouble that's brought on the world!).
You are only setting that child up for many future failures if they are not allowed to depend on their own knowledge. It is better for them to fail a test and regroup, acquire study skills that will take them further; than one teacher helping them.
I believe there are exceptions to rules but can't find where it would be ok to help a student cheat! I would also be interested in hearing from the side of yes-not to judge, just to get a different perspective!