Exclude one item from wp_list_pages( $args );

I have a menu that is currently shown with wp_list_pages( 'title_li=' );
This shows all the sub pages from all the pages in the menu.

I want to exclude a page with id 56 from displaying its sub items.

When I use wp_list_pages( 'exclude=56&title_li=' ); the menu becomes huge and all over the page.
When I use wp_list_pages( ‘exclude=56’ ); the menu gets messed up (vertical instead of horizontal (no li) and all of them are displayed.

How can I fix this?

There’s a filter called wp_list_pages_exclude that you could possibly hook into (put this in your functions.php):

function filter_wp_list_pages($exclude){
    $exclude[] = 56;
    return $exclude;
}

add_filter("wp_list_pages_excludes", "filter_wp_list_pages");