Sounds good in theory. But, I don't think these edu-pundits have thought through the ramifications of lowering the bar. Because when you lower the bar by an amount that seems reasonable, say to 85%, you wind up with a whopper of a problem. By lowering the bar you essentially foil the primary purpose of NCLB which is to "clos[e] the achievement gap between high- and low-performing children, especially the achievement gaps between minority and nonminority students, and between disadvantaged children and their more advantaged peers."
White students tend to outperform black students by about a standard deviation. But because these two populations are distributed normally, the percentile achievement gap between the two groups differs depending upon the difficulty of the testing instrument. Here is what the achievement gap looks like plotted against white pass rate.
As you can see, if we make the test sufficiently difficult such that no white students pass the exam, then we see that no black students will pass the exam either and the white/black gap is zero. We can achieve the same thing by making the exam so easy that all students pass it. This is shown at the white passing rate of 100%.
Setting the pass rate at zero would be political suicide. Setting the pass rate at 100% is NCLB--if all students pass the test the achievement gap is zero. (Of course, we'd like to see student achievement actually rise to the 100% level as opposed to merely decreasing the difficulty or cut score of the test, but I suppose in the real world we're going to get a little of both.)
Let's simply the issue and stipulate that it is politically feasible to set the the white pass rate at 50% or higher.
Looking at the graph, you quickly see that we have a big problem in that the achievement gap stays at a high level until we reach a 95% white pass rate, and even then the achievement gap is still likely to be at a politically unacceptable level.
Let's say we exclude all students in special education, about 13%, and require all non-special education students to pass the test. You can see from the graph that we're are still going to wind up with about a 25% gap which isn't exactly an improvement over the status quo.
The point of all this is that we have almost no room to play with NCLB's 100% pass rate before we negate the reason why we allow the feds any role in education in the first place--to address civil rights issues. Once we lower the pass rate a hair, the achievement gap will skyrocket which is an outcome the edupundits don't seem to appreciate.
Update: Here's another graph to help you visualize the achievement gap.
The top distribution is white distribution, while the bottom distribution is black distribution. You can picture how the gap increases as you hit the fat part of each distribution.