Posts from categories on pages

Hi!

Please help me, I made 3 pages and 3 subpages:
-About
– News
— My news
— News from the Internet
— Blogs
– Contacts

and 3 categories for news.

How to prevent news of the categories reflect on the relevant pages?

Now I realized this is so:
<? php if (is_page (6)) (query_posts ( “cat = 6”);)?>
…

But after this, subpages in sidebar is disappear.

Now i think, maybe, I did something wrong?

PS: Part for subpages in submenu:
global $notfound;
if (is_page() and ($notfound != ‘1’)) {
$current_page = $post->ID;
while($current_page) {
$page_query = $wpdb->get_row(“SELECT ID, post_title, post_status, post_parent FROM $wpdb->posts WHERE ID = ‘$current_page'”);
$current_page = $page_query->post_parent;
}
$parent_id = $page_query->ID;
$parent_title = $page_query->post_title;

if ($wpdb->get_results(“SELECT * FROM $wpdb->posts WHERE post_parent = ‘$parent_id’ AND post_type != ‘attachment'”)) {
?>
<li class=”widget”>
<h2><?php echo $parent_title; ?> <?php _e(‘Subpages’); ?></h2>
<ul class=”list-page”>
<?php wp_list_pages(‘sort_column=menu_order&title_li=&child_of=’. $parent_id); ?>

<?php } } ?>
But after that ceased to affect the internal pages in the left menu