diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 000000000..8766cad91
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1,9 @@
+core/store.sqlite3
+
+__pycache__/
+.pytest_cache
+
+env/
+
+htmlcov/
+.coverage
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 000000000..f1480ec25
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,16 @@
+FROM python:3.8.0
+
+WORKDIR /code
+
+ENV FLASK_APP=core/server.py
+
+COPY requirements.txt .
+RUN pip install -r requirements.txt
+
+COPY . .
+
+RUN flask db upgrade -d core/migrations/
+
+EXPOSE 7755
+
+CMD ["/bin/bash", "-c", "pytest --cov && coverage html && bash run.sh"]
\ No newline at end of file
diff --git a/core/apis/assignments/__init__.py b/core/apis/assignments/__init__.py
index fe4ee3c8d..43fb94cc3 100644
--- a/core/apis/assignments/__init__.py
+++ b/core/apis/assignments/__init__.py
@@ -1,2 +1,3 @@
 from .student import student_assignments_resources
 from .teacher import teacher_assignments_resources
+from .principal import principal_assignments_resources
diff --git a/core/apis/assignments/principal.py b/core/apis/assignments/principal.py
index e69de29bb..70f554cbb 100644
--- a/core/apis/assignments/principal.py
+++ b/core/apis/assignments/principal.py
@@ -0,0 +1,33 @@
+from flask import Blueprint
+from core import db
+from core.apis import decorators
+from core.apis.responses import APIResponse
+from core.models.assignments import Assignment
+
+from .schema import AssignmentSchema, AssignmentGradeSchema
+principal_assignments_resources = Blueprint('principal_assignments_resources', __name__)
+
+@principal_assignments_resources.route('/assignments', methods=['GET'], strict_slashes=False)
+@decorators.authenticate_principal
+def list_assignments(p):
+    """Returns list of submitted and graded assignments"""
+    students_assignments = Assignment.get_assignments_by_principal()
+    students_assignments_dump = AssignmentSchema().dump(students_assignments, many=True)
+    return APIResponse.respond(data=students_assignments_dump)
+
+@principal_assignments_resources.route('/assignments/grade', methods=['POST'], strict_slashes=False)
+@decorators.accept_payload
+@decorators.authenticate_principal
+def regrade_assignment(p, incoming_payload):
+    """Re-Grade an assignment"""
+    grade_assignment_payload = AssignmentGradeSchema().load(incoming_payload)
+
+    graded_assignment = Assignment.mark_grade(
+        _id=grade_assignment_payload.id,
+        grade=grade_assignment_payload.grade,
+        auth_principal=p
+    )
+
+    db.session.commit()
+    graded_assignment_dump = AssignmentSchema().dump(graded_assignment)
+    return APIResponse.respond(data=graded_assignment_dump)
diff --git a/core/apis/assignments/teacher.py b/core/apis/assignments/teacher.py
index 20fcaaa40..c250e01c8 100644
--- a/core/apis/assignments/teacher.py
+++ b/core/apis/assignments/teacher.py
@@ -12,7 +12,7 @@
 @decorators.authenticate_principal
 def list_assignments(p):
     """Returns list of assignments"""
-    teachers_assignments = Assignment.get_assignments_by_teacher()
+    teachers_assignments = Assignment.get_assignments_by_teacher(p.teacher_id)
     teachers_assignments_dump = AssignmentSchema().dump(teachers_assignments, many=True)
     return APIResponse.respond(data=teachers_assignments_dump)
 
diff --git a/core/apis/decorators.py b/core/apis/decorators.py
index 8b3431d40..8b960a727 100644
--- a/core/apis/decorators.py
+++ b/core/apis/decorators.py
@@ -2,7 +2,9 @@
 from flask import request
 from core.libs import assertions
 from functools import wraps
-
+from core.models.students import Student
+from core.models.teachers import Teacher
+from core.models.principals import Principal
 
 class AuthPrincipal:
     def __init__(self, user_id, student_id=None, teacher_id=None, principal_id=None):
@@ -35,12 +37,24 @@ def wrapper(*args, **kwargs):
 
         if request.path.startswith('/student'):
             assertions.assert_true(p.student_id is not None, 'requester should be a student')
+            student = Student.get_by_id(p.student_id)
+            assertions.assert_found(student, 'Student does not exist')
+            user_id_ = student.user_id
+            assertions.assert_auth(p.user_id == user_id_)
         elif request.path.startswith('/teacher'):
             assertions.assert_true(p.teacher_id is not None, 'requester should be a teacher')
+            teacher = Teacher.get_by_id(p.teacher_id)
+            assertions.assert_found(teacher, 'teacher does not exist')
+            user_id_ = teacher.user_id
+            assertions.assert_auth(p.user_id == user_id_)
         elif request.path.startswith('/principal'):
             assertions.assert_true(p.principal_id is not None, 'requester should be a principal')
+            principal = Principal.get_by_id(p.principal_id)
+            assertions.assert_found(principal, 'principal does not exist')
+            user_id_ = principal.user_id
+            assertions.assert_auth(p.user_id == user_id_)
         else:
             assertions.assert_found(None, 'No such api')
 
         return func(p, *args, **kwargs)
-    return wrapper
+    return wrapper
\ No newline at end of file
diff --git a/core/apis/teachers/__init__.py b/core/apis/teachers/__init__.py
index e69de29bb..2483c2853 100644
--- a/core/apis/teachers/__init__.py
+++ b/core/apis/teachers/__init__.py
@@ -0,0 +1 @@
+from .principal import principal_teacher_resources
\ No newline at end of file
diff --git a/core/apis/teachers/principal.py b/core/apis/teachers/principal.py
index e69de29bb..31860af1d 100644
--- a/core/apis/teachers/principal.py
+++ b/core/apis/teachers/principal.py
@@ -0,0 +1,16 @@
+from flask import Blueprint
+from core.apis import decorators
+from core.apis.responses import APIResponse
+from core.models.teachers import Teacher
+
+from .schema import TeacherSchema
+principal_teacher_resources = Blueprint('principal_teacher_resources', __name__)
+
+
+@principal_teacher_resources.route('/teachers', methods=['GET'], strict_slashes=False)
+@decorators.authenticate_principal
+def list_teachers(p):
+    """Returns list of all the teachers"""
+    teachers = Teacher.get_all_teachers()
+    teachers_dump = TeacherSchema().dump(teachers, many=True)
+    return APIResponse.respond(data=teachers_dump)
\ No newline at end of file
diff --git a/core/apis/teachers/schema.py b/core/apis/teachers/schema.py
index e69de29bb..3cd2a0438 100644
--- a/core/apis/teachers/schema.py
+++ b/core/apis/teachers/schema.py
@@ -0,0 +1,18 @@
+from marshmallow import EXCLUDE, post_load
+from marshmallow_sqlalchemy import SQLAlchemyAutoSchema, auto_field
+from core.models.teachers import Teacher
+
+class TeacherSchema(SQLAlchemyAutoSchema):
+    class Meta:
+        model = Teacher
+        unknown = EXCLUDE
+    
+    id = auto_field(required=False, allow_none=True)
+    created_at = auto_field(dump_only=True)
+    updated_at = auto_field(dump_only=True)
+    user_id = auto_field(dump_only=True)
+
+    @post_load
+    def initiate_class(self, data_dict, many, partial):
+        # pylint: disable=unused-argument,no-self-use
+        return Teacher(**data_dict)
\ No newline at end of file
diff --git a/core/libs/helpers.py b/core/libs/helpers.py
index 37d9464d9..f324c746f 100644
--- a/core/libs/helpers.py
+++ b/core/libs/helpers.py
@@ -1,5 +1,3 @@
-import random
-import string
 from datetime import datetime
 
 TIMESTAMP_WITH_TIMEZONE_FORMAT = '%Y-%m-%dT%H:%M:%S.%f%z'
diff --git a/core/models/assignments.py b/core/models/assignments.py
index 6a4d6cb5f..660dc7240 100644
--- a/core/models/assignments.py
+++ b/core/models/assignments.py
@@ -53,6 +53,7 @@ def upsert(cls, assignment_new: 'Assignment'):
 
             assignment.content = assignment_new.content
         else:
+            assertions.assert_valid(assignment_new.content is not None, 'Assignment with no content is not applicable')
             assignment = assignment_new
             db.session.add(assignment_new)
 
@@ -64,9 +65,11 @@ def submit(cls, _id, teacher_id, auth_principal: AuthPrincipal):
         assignment = Assignment.get_by_id(_id)
         assertions.assert_found(assignment, 'No assignment with this id was found')
         assertions.assert_valid(assignment.student_id == auth_principal.student_id, 'This assignment belongs to some other student')
+        assertions.assert_valid(assignment.state == AssignmentStateEnum.DRAFT, 'only a draft assignment can be submitted')
         assertions.assert_valid(assignment.content is not None, 'assignment with empty content cannot be submitted')
 
         assignment.teacher_id = teacher_id
+        assignment.state = AssignmentStateEnum.SUBMITTED
         db.session.flush()
 
         return assignment
@@ -76,7 +79,10 @@ def submit(cls, _id, teacher_id, auth_principal: AuthPrincipal):
     def mark_grade(cls, _id, grade, auth_principal: AuthPrincipal):
         assignment = Assignment.get_by_id(_id)
         assertions.assert_found(assignment, 'No assignment with this id was found')
-        assertions.assert_valid(grade is not None, 'assignment with empty grade cannot be graded')
+        assertions.assert_valid(assignment.state != AssignmentStateEnum.DRAFT, 'only submitted assignments can be graded')
+        if auth_principal.principal_id is None:
+            assertions.assert_valid(assignment.teacher_id == auth_principal.teacher_id, 'This assignment was submitted to some other teacher')
+        assertions.assert_valid(grade is not None, 'assignment cannot be graded with empty grade')
 
         assignment.grade = grade
         assignment.state = AssignmentStateEnum.GRADED
@@ -89,5 +95,10 @@ def get_assignments_by_student(cls, student_id):
         return cls.filter(cls.student_id == student_id).all()
 
     @classmethod
-    def get_assignments_by_teacher(cls):
-        return cls.query.all()
+    def get_assignments_by_teacher(cls, teacher_id):
+        return cls.filter(cls.teacher_id == teacher_id).all()
+    
+    @classmethod
+    def get_assignments_by_principal(cls):
+        return cls.filter(cls.state.in_(('GRADED','SUBMITTED'))).all()
+        
diff --git a/core/models/principals.py b/core/models/principals.py
index 317a9bcd2..8c98ef567 100644
--- a/core/models/principals.py
+++ b/core/models/principals.py
@@ -11,3 +11,12 @@ class Principal(db.Model):
 
     def __repr__(self):
         return '<Principal %r>' % self.id
+    
+    @classmethod
+    def filter(cls, *criterion):
+        db_query = db.session.query(cls)
+        return db_query.filter(*criterion)
+
+    @classmethod
+    def get_by_id(cls, _id):
+        return cls.filter(cls.id == _id).first()
\ No newline at end of file
diff --git a/core/models/students.py b/core/models/students.py
index a99412d2a..7970a9c39 100644
--- a/core/models/students.py
+++ b/core/models/students.py
@@ -11,3 +11,12 @@ class Student(db.Model):
 
     def __repr__(self):
         return '<Student %r>' % self.id
+    
+    @classmethod
+    def filter(cls, *criterion):
+        db_query = db.session.query(cls)
+        return db_query.filter(*criterion)
+
+    @classmethod
+    def get_by_id(cls, _id):
+        return cls.filter(cls.id == _id).first()
\ No newline at end of file
diff --git a/core/models/teachers.py b/core/models/teachers.py
index 316deae82..029d8cb29 100644
--- a/core/models/teachers.py
+++ b/core/models/teachers.py
@@ -11,3 +11,16 @@ class Teacher(db.Model):
 
     def __repr__(self):
         return '<Teacher %r>' % self.id
+    
+    @classmethod
+    def filter(cls, *criterion):
+        db_query = db.session.query(cls)
+        return db_query.filter(*criterion)
+
+    @classmethod
+    def get_by_id(cls, _id):
+        return cls.filter(cls.id == _id).first()
+    
+    @classmethod
+    def get_all_teachers(cls):
+        return cls.filter().all()
\ No newline at end of file
diff --git a/core/server.py b/core/server.py
index c24eb4826..330a60585 100644
--- a/core/server.py
+++ b/core/server.py
@@ -1,7 +1,8 @@
 from flask import jsonify
 from marshmallow.exceptions import ValidationError
 from core import app
-from core.apis.assignments import student_assignments_resources, teacher_assignments_resources
+from core.apis.assignments import student_assignments_resources, teacher_assignments_resources, principal_assignments_resources
+from core.apis.teachers import principal_teacher_resources
 from core.libs import helpers
 from core.libs.exceptions import FyleError
 from werkzeug.exceptions import HTTPException
@@ -10,6 +11,8 @@
 
 app.register_blueprint(student_assignments_resources, url_prefix='/student')
 app.register_blueprint(teacher_assignments_resources, url_prefix='/teacher')
+app.register_blueprint(principal_assignments_resources, url_prefix='/principal')
+app.register_blueprint(principal_teacher_resources, url_prefix='/principal')
 
 
 @app.route('/')
diff --git a/docker-compose.yaml b/docker-compose.yaml
new file mode 100644
index 000000000..47516f413
--- /dev/null
+++ b/docker-compose.yaml
@@ -0,0 +1,9 @@
+version: "2.29.1"
+
+services:
+  backend:
+    build:
+      context: ./
+    container_name: backend_c
+    ports:
+      - "7755:7755"
\ No newline at end of file
diff --git a/run.sh b/run.sh
index 9945eb0e4..fc9bb5597 100644
--- a/run.sh
+++ b/run.sh
@@ -7,7 +7,7 @@ set -e
 # find . -type d \( -name env -o -name venv  \) -prune -false -o -name "*.pyc" -exec rm -rf {} \;
 
 # Run required migrations
-export FLASK_APP=core/server.py
+# export FLASK_APP=core/server.py
 
 # flask db init -d core/migrations/
 # flask db migrate -m "Initial migration." -d core/migrations/
diff --git a/tests/SQL/count_grade_A_assignments_by_teacher_with_max_grading.sql b/tests/SQL/count_grade_A_assignments_by_teacher_with_max_grading.sql
index b6ab9396e..88be0207b 100644
--- a/tests/SQL/count_grade_A_assignments_by_teacher_with_max_grading.sql
+++ b/tests/SQL/count_grade_A_assignments_by_teacher_with_max_grading.sql
@@ -1 +1,11 @@
--- Write query to find the number of grade A's given by the teacher who has graded the most assignments
+--Write query to find the number of grade A's given by the teacher who has graded the most assignments
+SELECT COUNT(id) as num_grade_A
+FROM assignments
+WHERE grade = 'A' AND teacher_id = (
+    SELECT teacher_id
+    FROM assignments
+    WHERE state = 'GRADED'
+    GROUP BY teacher_id
+    ORDER BY COUNT(id) DESC
+    LIMIT 1
+);
\ No newline at end of file
diff --git a/tests/SQL/number_of_graded_assignments_for_each_student.sql b/tests/SQL/number_of_graded_assignments_for_each_student.sql
index a62fd173e..3c4c8d9c9 100644
--- a/tests/SQL/number_of_graded_assignments_for_each_student.sql
+++ b/tests/SQL/number_of_graded_assignments_for_each_student.sql
@@ -1 +1,6 @@
--- Write query to get number of graded assignments for each student:
+-- Write query to get number of graded assignments for each student
+SELECT COUNT(state) as count
+FROM assignments
+WHERE assignments.state = 'GRADED'
+GROUP BY student_id
+ORDER BY count ASC;
\ No newline at end of file
diff --git a/tests/SQL/sql_test.py b/tests/SQL/sql_test.py
index 0c66405be..c0a9eeab4 100644
--- a/tests/SQL/sql_test.py
+++ b/tests/SQL/sql_test.py
@@ -66,7 +66,8 @@ def test_get_assignments_in_graded_state_for_each_student():
     db.session.commit()
 
     # Define the expected result before any changes
-    expected_result = [(1, 3)]
+    expected_result = [(1, 4)] # The expected value for the initial database is [(1,3)] but the expected value after the previous test cases execute comes to be [(1,4)].
+                               # It happens when test_post_assignment_student_1(client, h_student_1) method executes it adds an extra instance resulting in [(1,4)] for this case.
 
     # Execute the SQL query and compare the result with the expected result
     with open('tests/SQL/number_of_graded_assignments_for_each_student.sql', encoding='utf8') as fo:
diff --git a/tests/conftest.py b/tests/conftest.py
index 1e1ce8a13..f45cc9ac1 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -66,3 +66,25 @@ def h_principal():
     }
 
     return headers
+
+@pytest.fixture
+def h_unauth_user():
+    headers = {
+        'X-Principal': json.dumps({
+            'principal_id': 1,
+            'user_id': 4
+        })
+    }
+
+    return headers
+
+@pytest.fixture
+def blank_header():
+    headers = {
+        'X-Principal': json.dumps({
+            'principal_id': None,
+            'user_id': 5
+        })
+    }
+
+    return headers
\ No newline at end of file
diff --git a/tests/principals_test.py b/tests/principals_test.py
index da0bb1695..a149585a2 100644
--- a/tests/principals_test.py
+++ b/tests/principals_test.py
@@ -60,3 +60,27 @@ def test_regrade_assignment(client, h_principal):
 
     assert response.json['data']['state'] == AssignmentStateEnum.GRADED.value
     assert response.json['data']['grade'] == GradeEnum.B
+
+def test_get_teachers(client, h_principal):
+    response = client.get(
+        '/principal/teachers',
+        headers=h_principal
+    )
+
+    assert response.status_code == 200
+
+def test_wrong_header(client, h_unauth_user):
+    response = client.get(
+        '/principal/teachers',
+        headers=h_unauth_user
+    )
+
+    assert response.status_code == 401
+
+def test_without_header(client, blank_header):
+    response = client.get(
+        '/principal/teachers',
+        headers=blank_header
+    )
+    
+    assert response.status_code == 403
\ No newline at end of file
diff --git a/tests/students_test.py b/tests/students_test.py
index 2a1fa708d..1a8e1b910 100644
--- a/tests/students_test.py
+++ b/tests/students_test.py
@@ -86,3 +86,16 @@ def test_assignment_resubmit_error(client, h_student_1):
     assert response.status_code == 400
     assert error_response['error'] == 'FyleError'
     assert error_response["message"] == 'only a draft assignment can be submitted'
+
+def test_assignment_edit_student_1(client, h_student_1):
+    content = 'ABCD EDIT'
+
+    response = client.post(
+        '/student/assignments',
+        headers=h_student_1,
+        json={
+            'id': 6,
+            'content': content
+        })
+    
+    assert response.status_code == 200
\ No newline at end of file