public function is_disabled() {
        $lockedgrade = $lockedgradeitem = 0;
        if (!empty($this->grade->locked)) {
            $lockedgrade = 1;
        }
        if (!empty($this->grade->grade_item->locked)) {
            $lockedgradeitem = 1;
        }
        return ($lockedgrade || $lockedgradeitem);
    }