change the code order:
$updateSQL = "UPDATE teacher SET booklist = 1 WHERE teacherID = '".$_SESSION['id']."'");
$update_CMD = mysql_query($updateSQL, $WA_connection) or die(mysql_error());
$_SESSION[$WA_sessionName] = mysql_insert_id($WA_connection);
to:
$_SESSION[$WA_sessionName] = mysql_insert_id($WA_connection);
$updateSQL = "UPDATE teacher SET booklist = 1 WHERE teacherID = '".$_SESSION['id']."'");
$update_CMD = mysql_query($updateSQL, $WA_connection) or die(mysql_error());