how to change site tag line for particular pages

If your theme is using the WordPress site tagline, you should be able to filter it. get_bloginfo( 'description' ) will call get_option( 'blogdescription' );, and we can filter the value of an option using the option_{$option} hook.

Let’s suppose, for this code sample, that you want to change the tagline on 3 pages, with the titles Kindergarten, Nursery School, and Babysitting.

add_filter( 'option_blogdescription', 'wpse368031_change_tagline' );
function wpse368031_change_tagline( $tagline ) {
    $pages = array( 'Kindergarten', 'Nursery School', 'Babysitting' );
    if ( is_page( $pages ) ) {
        $tagline="ABC Nursery";
    }
    return $tagline;
}

Try adding this code to your active theme’s functions.php file.

Reference

• get_bloginfo( 'description' )
• option_{$option} hook
• is_page()