Predicting child criminals have become a useful method in preventing child from becoming criminals like in minority report. The one question is that what if they don't want to be "cured" and like/accept who they are. It seems to me that this is a grey area.
It's harmful because it supposes three items of knowledge which we do not, and arguably cannot have:
1 Accurate predictions of future behavior
2 Knowledge of the right way to "fix" a criminal inclination
3 The larger social implications of "fixing" criminals in childhood
1 - Assuming that people make any significant choices in life, we have to believe that future criminal activity is not fully determined by childhood characteristics. At most, we could determine that some people have a greater probability of criminal action. Are we justified in tampering with people in the case it's only a probability, not a certainty?
2 - At one time, an accepted and alarmingly common medical procedure for mental issues was to remove part of the brain --often with disastrous results. How sure are we that we know the correct way to correct criminal inclinations?
3 - New research suggests that (for instance) the extreme lack of empathy we associate with sociopathy can in some cases lead to high-achievement, not criminal behavior --for instance, many CEOs are somewhat sociopathic. How do we know that fixing child criminals might not have unforeseen negative consequences for society as a whole?
Because those in charge of "predicting and correcting" bad behaviour often pursue their own selfish purposes in "predicting and correcting".
This documentary highlights several ways how American public schools consistently harming the kids attending public schools by putting numerous vibrant kids on dangerous mind-altering drugs, by vilifying kids for harmless behaviour, etc. Many "predicting and correcting" policies imposed by the teachers' union serve nobody but the teachers, making their lives less stressful, and simultaneously destroying the kids.
The drugs pushed on American kids temporarily make the kids easily manageable in the classroom vegetables, but lead to long-term behavioural and medical problems. Most of the school shootings in the US was done by kids that took Ritalin or other psychotropic drugs at one time or another, ironically imposed by the school they later shot at. And yet US public schools are almost forcibly pushing these drugs on the kids at rates higher than in other civilized country by orders of magnitude.
The only reason for that: while diagnosing and "treating" the kids the school-employed psychiatrists pursue the interest of the public schools, not the kids. The teacher doesn't want to deal with a vibrant kid because a quiet complacent class is less stressful. The teacher reports her "concerns" to the school; the school psychologist refers the kid to a psychiatrist; the psychiatrist is motivated in a number of ways to prescribe Ritalin, and the vibrant kid, one of those who would later make a dent in the Universe, ends up flipping burgers for the rest of his life, trying to cope with severe lifelong side effects.