These people were men and women of God who have earnestly built Christ-centered homes with lots of love. The fact that some of their children have departed from the faith cannot be blamed on the training program. No, this solution does not give a satisfactory answer to the cases of young adults from fine Christian homes who have rebelled and departed from the faith. Children need help and direction in order to develop their God-given talents. We need to look further for the full answer as to why, at times, this proverb seems not to hold true.
Proverbs are general truths stated in general terms.
A proverb is not a precept. A precept is a truth stated in absolute terms. An illustration may help here. Suppose we are making statements of truth about engineering students at a particular university. That statement of truth is in precept form.