jQuery(document).on('lrm_user_logged_in', function(response, $form, action) {
    if ( "register"=== action && response.data.user_id && $(".um-153").length > 0 ) {
    // $(".um-153").length > 0 is optionally to check if your form is loaded on the page, like

     // DO your ACTION like
      my_send_teacher_msg(response.data.user_id);
    }
});