The WTS has never come close to fulfilling this scripture at any time in it's history, even if you view this scripture as a general rule. Not even children of elders, who receive a regular one hour per week Bible study, stay in. As noted above, about 2/3 of young people are gone by the time they get into adulthood.
That's because the Devil is working harder knowing he only has a short time left.
Sorry, but your rationale is flawed and full of excuse-making. Prov 22:6 is an assurance given by the Creator, and his word is flawless, don't you believe that? Certainly holy spirit is a stronger force than the Devil. Those inspired words are a protection from the very thing you are yielding to in your answer. You are actually tipping your hat to Satan as being stronger than Jehovah.
The fact that JW children fall away from the religion proves one of two things. Either JW parents are guilty of not bring up their children 'according to the way for them', or the religion itself is not the right way. Since even children of elders, who must conduct a one-hour per week family study with them, fall away, it strongly suggests that the religion is not the right way.
Thankfully the Slave Class saw fit to institute Family Worship Night as a counteracting measure against the machinations of the Devil.
According to your Watchtower-sympathyzing way of thinking, the Family Worship Night will eliminate your young people from leaving the organization, and JWs will finally start fulfilling Prov 22:6? After more than 130 years of being in existance? That's what the family study was for all along, isn't it? It didn't work. Surely you can't be so naive as to think that changing the name to FWN will make any difference. Since it was instituted has there been any real change in the young ones leaving?
What will you say after 10 years pass, and young ones still leave? What if they are leaving in even greater numbers than now? What new excuses will you have?