function addTeacher(Teacher $teacher)
 {
     $connectionObject = Connection::getInstance();
     $connection = $connectionObject->get_connection();
     $name_in_full = $teacher->getName();
     $subject = $teacher->getSubject();
     $address = $teacher->getAddress();
     $telephone = $teacher->getPhoneNumber();
     $registered_date = $teacher->getRegisteredDate();
     $distance = $teacher->getDistance();
     $school_id = $_SESSION['school_id'];
     $stmt = $connection->prepare("INSERT INTO teacher (name_in_full, subject, address,  telephone) VALUES (?,?,?,?)");
     $stmt->bind_param("ssss", $name_in_full, $subject, $address, $telephone);
     $result = $stmt->execute();
     $stmt->close();
     $teacher_id = mysqli_insert_id($connection);
     $stmt = $connection->prepare("INSERT INTO teacher_school (teacher_id,school_id,start_of_working_date,distance_from_permanent_residence) VALUES (?,?,?,?)");
     $stmt->bind_param("iisi", $teacher_id, $school_id, $registered_date, $distance);
     $result = $stmt->execute();
     $stmt->close();
     return $result;
 }