–What is the gentlest way to restrain underclass reproduction?–
The gentlest way to restrain underclass reproduction is to be honest about it, transfer from services to direct redistribution, and to make redistribution contingent on single child reproduction, and offer free sterilization after the fist birth, and require sterilization of those with severe histories in the family (we have studies on this it’s pretty obvious stuff).
And secondly to limit immigration to those with IQ’s 125 and above.