I don't like the selective system, because
[1] it assumes that most children matures at a similar rate at a narrow point of time in year 6. Sure there are chances later but in the main that's when most people get in.
[2] It put children in a hot house situation when they should be more free to just play, which i *feel* impacts on life long stress and creativity levels
[3] Sport must miss out somewhat
[4] It monetizes a whole sub culture of swat schools, which feeds back into public schools slacking off as they "see" students are doing well no matter what they do. So the taxpayer as usual has to pay twice.
[5] Children are always studying rather than enjoying life a ta time when life should be really really enjoyable
[6] Your marks are scaled by your cohorts performance, so if your at a academically poor school unless your a few standard deviations out your screwed. This has synergy with [1].