Sadly there will never be a solution. The best option I can think of would never be allowed. I think anyone who abuses a child should be shot the second they are found guilty. After doing that a few times others would think a little more before hurting a child.
Parents could either be required or be given an incentive to attend parenting classes. While this may not guarantee that their children won't be abused, it may help them learn other ways to cope. There really isn't too much you can do to prevent abuse if you don't know that it's happening. Another thing that could be done is that monitors be put throughout schools and parents be allowed to check in on their children over a monitor in the school or over the internet. People can train their children through "What if?" things or show them examples of what abuse looks like and what to do and who to tell if something happens to them.
The best we can do right now its to be there for the children who have gone through this...if we know-or suspect-this is happening, report it as soon as possible...a for preventing it....I agree with peeples- shot a few of these monsters and maybe this madness will at least slow down....
We could do what China does and limit the number of children any individual or couple can have. We could one up it by requiring parents to carry a parenting license that has to be renewed every two years. People wishing to have a child must go through infant parenting classes prior to getting pregnant and must take continuing parenting classes when renewing their parenting license.