I can understand the sentiment. I've seen some real problem children, and I'm sure there could be many horror stories told. But my first thought is that there was a similar philosophy applied to the concept of voting in the U.S., with rather disastrous results. So disastrous, in fact, that they were made illegal via constitutional amendment. I'm not quite sure the same problems would apply to this case, but perhaps the same questions should be raised nevertheless.
The general idea seems to stem from the general philosophy that a standardized test of some sort is the best way of measuring whatever is at issue, and I would think that most people would know that the main problem is that such tests tend to prove something completely unrelated to the subject at hand. Perhaps testing in some manner isn't really the answer.
Perhaps the real question that needs to be addressed, though, is whether this is an actual solution. After all, one could certainly posit that the general number of foolish parents would not have necessarily risen over the course of hundreds of years, yet, here we are. Maybe the problem is not that the parents themselves are ignorant, but they just don't have the time necessary to raise children, which would really be a problem with contemporary society.
But then, maybe this is something we don't need to worry about. Maybe the horror stories are extremely rare, and we just notice them because they are so horrific. If so, there is still a problem, but one that will never be fixed, and can't really be handled in any suitable fashion.