Take a look (link below) at emerging fallouts of one such large-scale testing based improvement programme, enacted through the No Child Left Behind law in the US.
82 percent of US schools may be labeled 'failing'
Admittedly, this is only a news report, and there are also defenders, but the difficulties being faced by schools are real. There is also no evidence that whatever improvements that might have been brought about are long lasting, or that the nature of classroom processes and relationships has improved, or that children and teachers both find the school more worth coming to.
If you're an administrator or accountability activist or from an organisation that funds educational efforts - do consider that you might be doing yourself a disservice by insisting on testing as the means of assessing impact or of ensuring improvement. There's a lot more to education in the 21st century, and it does not lend itself to such simplistic frames!