Show child pages on front page using odd/even classes

Hi, I’m no WordPress/PHP expert, and I’m using this piece of code with the Twenty Ten theme to show the child pages of a parent page on the front page of my site, but it’s only showing 5 pages instead of the 10 that are there. Anyone know why?

<div class="options">
		<ul class="clearfix">
	<?php $i = 1; ?>
	<?php
$post_per_page = 10;
$args = array(
		'post_parent' => $post->ID='11',
		'post_type' => 'page',
		'post_status' => 'publish',
		'post_per_page' => $post_per_page
		);
		$postslist = get_posts($args);
		foreach ($postslist as $post) :
		setup_postdata($post);
	?>
			<?php if($i%2 == 0) : ?>
			<li id="<?php echo $post->post_name; ?>" class="nomarr">
			<?php else : ?>
			<li id="<?php echo $post->post_name; ?>">
			<?php endif; ?>
		        <?php $i++; ?>
				<a class="icn" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a>
				<h2><?php the_title(); ?></h2>
				<?php echo get_field('description'); ?>
			</li>
	<?php endforeach; ?>
		</ul>

         </div>

Thanks in advance for any help.