I need protect my Joomla! articles using de ACL + MembershipPro

Question

I have site that the restriction menus and categories fuciona well.

Articles when I use the URL directly into the browser (outside the restricted area) are shown.

Tried using finte below to resolve the problem temporarily ...

com_content \ Controller.php:

$user = JFactory::getUser();
$groups = $user->get('groups');
$is_aluno = in_array('11', $groups);

if !($is_aluno) {
    return JError::raiseError(403,JText::sprintf('JLIB_APPLICATION_ERROR_UNHELD_ID', $id));
}

Thanks!