Updating Schema File

I am trying to edit the roles and capabilities in the schema file to change how private posts are handled (so all users can read private posts), but after I edit and upload the schema.php file in /wp-admin/includes/ I don’t see any changes taking affect in the blog. Am I missing a step? I do not see that the schema information for capabilities and roles is written to the db, so I’m not sure what else to do.

An example of the added code:

$role = get_role(‘subscriber’);
if ( ! empty($role) ) {
$role->add_cap(‘read_private_posts’);
$role->add_cap(‘read_private_pages’);
}

Thanks!