The problem with that in America is that allowing entrance to schools based entirely on tests scores results in large numbers of Asians and whites and very few black and Hispanics and you end up with this racial discrimination mess.
The current system ensures that the people who need the most help get the least.
West Wing had a nice conversation about this with regard to Affirmative Action beteen the black intern and the conservativx supreme court justice.
So yeah, I feel like I got negative value out of my public school experience. But, my mother was a teacher; and she taught me to read and supplied me with books. Without reading as much as I did? I would have gotten nowhere. My dad? mid-level IT manager. My step dad? a computer programmer. I had access to computers from the age of three, programming environments, and parents who would help me learn about that shit.
My experience would indicate that the children of people who don't have valuable skills to pass on to their children would benefit much more from a public school "education" than I could.
My friend was diagnosed with multiple learning disabilities as a child, and attended a school for people like him. Classes were small, teachers understood and he learned how to write and do math as well as an ordinary person- great results for someone with his long list of disabilities.
On the other hand, I aced an exam to go to a very selective school. Teachers pushed every kid there to do their best, and I learned how to speak, write, debate, program and do math at a level far beyond what I would have otherwise. Sure, I would have come out of my high school years knowing a lot about math no matter what school I attended, but I wouldn't have learned anything about how one should speak or debate, nor would I have learned how to write well.
I think that's the way to go- push kids as far as they can go. This is a lot easier when teachers know how far they can push, which is where results- based stratification ( something I, at least, consider synonymous to merit-based) comes in.