Pittsburgh has instituted a school policy that no child can score less than 50% on any test, assignment or any other graded work. If the score would be less than 50% it is automatically adjusted up to this cut-off limit.
The reason is to give severely failing students a reason to keep trying; somebody with a 20% score on the first semester would no longer need almost 100% on the remaining semester to pass any more. That won't really work of course, as somebody with the skills and background knowledge to manage only a 20% or 30% score during one semester has no more chance of making 70% or 65%(the needed score) the next semester than they would have had making 100% or 90%. There's a reason the student was failing badly in the first place, and with later material depending on the failed, previous material this is not going to make much of a difference. All it does is mask the problems for a little while longer until the student fails even the new, inflated level.
They could have achieved the same thing by simply adjusting the grade levels downward, with a passing grade at 40-45% rather than 60%. That would have had the benefit of honesty and openness, and would signal that yes, we do value your work even when the score is low. Placing an artificial floor like this, on the other hand, signals that what you do below a certain point simply doesn't matter. Do nothing but make funny noises throughout the test, or work hard and get half right - it's exactly the same as far as the school is concerned. So, if you're going to fail exactly equally in either case, why not spend your time practising your musical burping rather than study for the test?
It never ceases to amaze me how creative people can be when it comes to screwing up the school system, in any country.