Filter, PHP, Search | Type: PHPHiding Specific Pages and Posts

Add to theme functions file:

function exclude_specific_posts_from_search($query) {
  // Check if it's a front-end search query (not admin)
  if ($query->is_search && !is_admin()) {
    // Replace 123, 456 with your page/post IDs to exclude
    $excluded_ids = array(123, 456); 
    $query->set('post__not_in', $excluded_ids);
  }
}
add_action('pre_get_posts', 'exclude_specific_posts_from_search');