Does a godly upbringing stop a person from succumbing to the old Adamic nature?
No. A godly home and good parents can teach inhibitions and certain behaviors to a degree, but no human endeavor can break the old Adamic nature's control. Even the best person still gives in. Only God's power, through being crucified with Christ, frees a person from that control.
Les explains that good parents and a godly home can teach children a certain amount of inhibitions and moral conduct, but that only goes so far. No human endeavor can break the control of the old Adamic nature; only the power of God can do it. Eventually, even in the best person's life, there comes a point when they still give in to old Adam. The only way out from under that control is for Adam to die and be crucified. Les connects this to Galatians 2:20, where Paul says, "I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me." That is the new life, the new creation spoken of in 2 Corinthians chapter 5.