So what you're saying is that parents should pass more than the
practical test to parenthood?
I agree with you in principle in terms of raising well-balanced children but my one concern is how to decide who is an appropriate parent and who isn't. What if some beaurocrat decided that black people don't make good parents?
In any case, overpopulation is not a good enough reason for this. A law like this would only apply in the western world, where birth rates have been dropping anyway, to the point that many countries need immigration just to keep a constant population.