protected function getSecondLevelPages()
    {
        $secondLevel = array();

        foreach ($this->topLevelPages as $topLevelPage) {
            $pages = get_posts(array(
                'post_parent' => $topLevelPage->ID,
                'post_type' => 'page',
                'orderby' => 'menu_order post_title',
                'order' => 'asc',
                'posts_per_page' => -1
            ));

            $secondLevel[$topLevelPage->ID] = $pages;
        }

        $this->secondLevelPages = $secondLevel;
        return $secondLevel;
    }