编写程序，创建学生成绩中所涉及的类： `Student` 类、 `Teacher` 类、 `Course` 类，并由 `Grade` 类将 `Student` 类、 `Teacher` 类和 `Course` 类关联起来，由 `GradeTest` 类对以上四个类进行测试。

好的，这是一个比较复杂的问题，需要分别实现四个类。以下是我编写的代码，供你参考：

# 定义学生类
class Student:
    def __init__(self, name, id):
        self.name = name
        self.id = id
        self.courses = []

    def add_course(self, course):
        self.courses.append(course)

# 定义教师类
class Teacher:
    def __init__(self, name, id):
        self.name = name
        self.id = id
        self.courses = []

    def add_course(self, course):
        self.courses.append(course)

# 定义课程类
class Course:
    def __init__(self, name, id, teacher):
        self.name = name
        self.id = id
        self.teacher = teacher
        self.students = []

    def add_student(self, student):
        self.students.append(student)

# 定义成绩类
class Grade:
    def __init__(self, course, student, score):
        self.course = course
        self.student = student
        self.score = score

# 定义测试类
class GradeTest:
    def __init__(self):
        self.students = []
        self.teachers = []
        self.courses = []
        self.grades = []

    def add_student(self, name, id):
        self.students.append(Student(name, id))

    def add_teacher(self, name, id):
        self.teachers.append(Teacher(name, id))

    def add_course(self, name, id, teacher_id):
        teacher = None
        for t in self.teachers:
            if t.id == teacher_id:
                teacher = t
                break
        if not teacher:
            raise ValueError("Teacher not found")
        course = Course(name, id, teacher)
        teacher.add_course(course)
        self.courses.append(course)

    def add_grade(self, course_id, student_id, score):
        course = None
        for c in self.courses:
            if c.id == course_id:
                course = c
                break
        if not course:
            raise ValueError("Course not found")
        student = None
        for s in self.students:
            if s.id == student_id:
                student = s
                break
        if not student:
            raise ValueError("Student not found")
        grade = Grade(course, student, score)
        course.add_student(student)
        self.grades.append(grade)

    def print_grades(self):
        for grade in self.grades:
            print("{0} {1} {2} {3}".format(grade.course.name, grade.student.name, grade.score, grade.course.teacher.name))

这个程序中，`Student` 类、 `Teacher` 类、 `Course` 类分别表示学生、教师和课程，`Grade` 类表示成绩。`Grade` 类将 `Student` 类、 `Teacher` 类和 `Course` 类关联起来，通过 `GradeTest` 类进行测试。`GradeTest` 类中包含了添加学生、教师、课程和成绩的方法，以及打印成绩的方法。你可以根据自己的需求进行修改和扩展。