Worpress allows you to print parent menu’s with different child-menus. Implementation is easy, just add this to your themes.

In the file that creates the header of your page, normally header.php, add this code:

     <?php   $args = array(

            'title_li' => '',

            'sort_column'=>'menu_order',

            'depth' => 1

                  );

    wp_list_pages($args);

    ?>

Then in the file that creates your child menu (normally this should be sidebar.php) add this code:

   <?php

  if($post->post_parent) {

    $children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");

  }

  else {

    $children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");

  }

  if ($children) { ?>

    <ul>

      <?php echo $children; ?>

    </ul>

  <?php } ?>

The selected menus are li.current_page_parent and li.current_page_item so you should adjust their style in your stylesheet.