Hmm, I found this.
24
Thereafter, what would parents do in behalf of their erring minor child? They are still responsible for their child, though he is disqualified as an unbaptized publisher or even if he is disfellowshipped because of wrongdoing after baptism. Just as they will continue to provide him with food, clothing, and shelter, they need to instruct and discipline him in line with God’s Word. (Proverbs 6:20-22; 29:17) Loving parents may thus arrange to have a home Bible study with him, even if he is disfellowshipped. Maybe he will derive the most corrective benefit from their studying with him alone. Or they may decide that he can continue to share in the family study arrangement. Though he has gone astray, they want to see him return to Jehovah, as did the prodigal son in Jesus’ illustration.—Luke 15:11-24.
It seems that minor children are still to be tortured by Bible studies, but once they reach that magical age of 18 the rule does a complete 180 and they can't even be present at the bible study? Madness!