When you base policy on "data" and discount "soft" information such as personal testimony, the hallmark of the Duncan Regime in the US Department of Education, you can produce a policy disaster of epic proportions. Why? Because data can be easily manipulated by self-interested parties. No better example of this can be found than in the sub prime mortgage crisis where Moody's and Standard and Poors gave triple A ratings to bundled mortgages, each of which, on its own, was in grave danger of foreclosure. The same kind of "cooking the books" is taking place in education policy where charter schools are extolled as producing superior test results to public schools, and given preferential treatment, even though they expel or push out students who don't test well.
If you aren't on the ground, taking testimony about what the statistics hide as well as what they reveal, you will never know when your policies end up doing far more harm than good.
Failure to do that is why Arne Duncan is likely to be remembered as the worst Secretary of Education in US History, and the Presidency of Barack Obama as nightmare of false homes and shattered dreams for America's teachers.