This is not only scientifically inaccurate, but it's also morally incoherent. Children are children because they are not fully developed human beings. Science tells us that adolescents are biologically driven to embrace risky and stupid behavior. The part of the brain called the prefrontal cortex, which actually controls for risky behavior, isn't fully developed until children are fully grown. Leave children and adolescents to their own devices, and they will not make good decisions -- they will attack any boundaries and cross any lines.
What is government's role in all of this? Justice Scalia believes that government should not put more power in the hands of parents -- government should essentially be neutral between children and those who raise them. Justice Thomas believes that government should create a system wherein parents get the last word. In today's world, more than ever, it is important that children not be treated with libertarian casualness requiring parents to be all-knowing and all-seeing. Instead, government should place control firmly in the hands of parents, requiring children to go to their parents for advice and guidance.
Freedom and responsibility for actions go hand in hand; only adults can be held responsible for their actions and the actions of their children. Therefore, only adults should have the freedom to choose on behalf of their children. Any other moral system is a fundamental rejection of the superstructure of civilization in favor of a moral chimera.