from django.db import models
from django.contrib.auth.models import BaseUserManager, AbstractBaseUser



class User(AbstractBaseUser):
    email = models.EmailField(
    verbose_name='email address',
    max_length=255,
    unique=True,
    )
    date_of_birth = models.DateField(null=True)
    is_active = models.BooleanField(default=True)
    is_admin = models.BooleanField(default=False)
    is_teacher = models.BooleanField(default=False)
    is_student = models.BooleanField(default=False)
    is_parent = models.BooleanField(default=False)
    in_class= models.BooleanField(default=False)
    bio = models.TextField(blank=True, help_text='write something about
    yourself...')
    # goes on...

from django.db import models
from accounts.models import User
from django.db.models.signals import post_save, pre_save
from django.dispatch import receiver


class GroupOfStudents(models.Model):
    teacher = models.ForeignKey(User,on_delete=models.CASCADE)
    students = models.ManyToManyField(User, related_name='students')

    def __str__(self):
        return "Class of Teacher {}".format(self.teacher.first_name)

@receiver(post_save, sender=GroupOfStudents)
def change_teacher_inclass(sender, instance, created, **kwargs):
    if created:
        teacher = instance.teacher
        teacher.in_class=True
        teacher.save()

@receiver(post_save, sender=GroupOfStudents)
def change_student_inclass(sender, instance, created, **kargs):
    if created:
        for student in instance.students.all():
            student.in_class=True
            student.save()

>>> from accounts.models import User
>>> from klass.models import GroupOfStudents
>>> g = GroupOfStudents.objects.all()
>>> first_obj = g[0]
>>> first_obj
<GroupOfStudents: Class of Teacher teacher>
>>> for user in User.objects.filter(is_student=True):
...     if user in first_obj.students.all():
...         user.in_class = True
...         user.save()

If usere.email == student.email:
#same stuff of inclass....