Page not found when trying to link to files in child theme directory

Shouldn’t you be enqueuing that in functions.php instead?

function script_enqueueing() {
    wp_enqueue_script(
        'scripts',
        get_stylesheet_directory_uri() . '/js/scripts.js',
        array('jquery')
    );
}
add_action('wp_enqueue_scripts', 'script_enqueueing');

Edit to add: if calling directly in header.php, use get_template_directory_uri(); instead.