$wpdb->query("UPDATE $tablePerson SET school_list = CONCAT (school_list, $school_post_id) WHERE autor_id = $userId");
$sql = $wpdb->prepare("UPDATE %s SET school_list = CONCAT (school_list, %s) WHERE autor_id = %d", $tablePerson, $school_post_id, $userId );
$result = $wpdb->query( $sql );