Password protect child pages so you don't have to create a password for each page.

wp_password_protect_children.php

<?php
/**
 *  Create a custom length content string.
 *
 *  @param   integer  post  ID of the parent page
 *  @return  void
 */
function wp_password_protect_children( $post ){
	foreach( get_post_ancestors( $post ) as $parent ) {
		if( post_password_required( $parent ) ) {
			$location = get_permalink( $parent );
			wp_redirect( $location );
			exit;
		}
	}
}
add_action( 'template_redirect', 'password_protect_children' );