Copying Relations Between Models

I'm trying to create a system that automatically generates lessons based upon a rule I've created using database fields. The rule would hold a list of students and teachers as many-to-many relationships.

I want to directly transfer the relations from the course instance to the lesson instance through a post_save signal.

These are my models

class Course(models.Model):
    students = models.ManyToManyField(
        Profile,
        limit_choices_to=Q(is_teacher=False),
        related_name='course_students')
    teachers = models.ManyToManyField(
        Profile,
        limit_choices_to=Q(is_teacher=True),
        related_name='course_teachers')

class Lesson(models.Model):
    students = models.ManyToManyField(
        Profile,
        limit_choices_to=Q(is_teacher=False),
        related_name='lesson_students')
    teachers = models.ManyToManyField(
        Profile,
        limit_choices_to=Q(is_teacher=True),
        related_name='lesson_teachers')

This is my signal code

@receiver(post_save, sender=Course)
def new_course_lesson_creator(sender, instance, created, **kwargs):
    if not created:
        return
    print "Course Created!"
    teachers = instance.teachers.all()
    students = instance.students.all()
    lesson = Lesson()
    lesson.teachers.add(*teachers)
    lesson.students.add(*students)
    lesson.save()

For whatever reason this doesn't transfer the related student and teacher relations to the lesson. The "teachers" and "students" show up as empty.

Any and all help is appreciated :)