changing “older/newer posts” wording on search results page

I am trying to change “older/newer posts” wording on the search results page. I have tried to do this by placing the following in functions.php in my theme folder:

/*...............
Changing "older/newer posts" wording for search results page
...............*/
add_filter('twentytwelve_content_nav', 'mychild_theme_content_nav');
if (is_search()) {
function mychild_theme_content_nav( $html_id ) {
	global $wp_query;
	$html_id = esc_attr( $html_id );
	if ( $wp_query->max_num_pages > 1 ) : ?>
		<nav id="<?php echo $html_id; ?>" class="navigation" role="navigation">
			<h3 class="assistive-text"><?php _e( 'Post navigation', 'twentytwelve' ); ?></h3>
			<div class="nav-previous alignleft"><?php next_posts_link( __( '<span class="meta-nav">&larr;</span> less relevance to the search', 'twentytwelve' ) ); ?></div>
			<div class="nav-next alignright"><?php previous_posts_link( __( 'more relevance to the search <span class="meta-nav">&rarr;</span>', 'twentytwelve' ) ); ?></div>
		</nav><!-- #<?php echo $html_id; ?> .navigation -->
	<?php endif;
						}
}

Alas, the “older/newer post” links at the bottom of the search results page persists. Any ideas what I’ve done wrong with my coding?

Thank you.

-E Morris, etherwork [dot] net [slash] blog <<purposely unlinked in attempt to keep spammers at bay (there’s a really good reason that I have iThemes Security plugin who helped enormously to rid me of bruteforce attacks)