public function insertUser($userName, $userSurname, $userEmail, $userPassword, $userSchool, $userGrade, $userIdNumber, $userContact){
        $sql = "INSERT INTO edge_tuition.users(userName = ?, userSurname = ?, userEmail = ?, userPassword = ?, "
            . "userSchool = ?, userGrade = ?, userIdNumber = ?, userContact = ?)";
        $stmt = $this->dbConnection->prepare($sql);
        $stmt->bind_param("ssssssss", $userName, $userSurname, $userEmail, $userPassword, $userSchool, $userGrade, $userIdNumber, $userContact);
        if ($stmt->execute()){
        return true;
        }else {
            return false;
        }
    }