I have a question about COPPA

[BSMedia]

The line you probably want to change is on 174 of register.php

 if ($vbulletin->GPC['year'] < 1970 OR (mktime(0, 0, 0, $vbulletin->GPC['month'], $vbulletin->GPC['day'], $vbulletin->GPC['year'])
 <= mktime(0, 0, 0, $current['month'], $current['day'], $current['year'] - 13)))

change 13 to 18 and that should probably do it. Though I didn't test this so be sure to backup your register.php