In that case try to create custom sql query like this.
global $wpdb;
$query = "SELECT meta_value FROM wp_postmeta WHERE post_id=your post id AND meta_key='class';
$results = $wpdb->get_row($query) ; echo $results->meta_value;
In that case try to create custom sql query like this.
global $wpdb;
$query = "SELECT meta_value FROM wp_postmeta WHERE post_id=your post id AND meta_key='class';
$results = $wpdb->get_row($query) ; echo $results->meta_value;