RSpec Expectations and ExpectationNotMetError

Hello I have been following a course to further my understanding of cucumber. The course is a little old so i have had to update some rspec syntax from should to expect but otherwise have been following it very carefully. I cannot get this recent test to pass and i am rather lost as to why. The error i am receiving is below. I understand it is receiving nil when it should be receiving 95 but i still do not understand why.

When They submitted an assignment    # features/step_definitions/teacher_grade_assignment.rb:6
    Then the assignment has a grade      # features/step_definitions/teacher_grade_assignment.rb:14

      expected: 95
           got: nil

      (compared using ==)
       (RSpec::Expectations::ExpectationNotMetError)
      ./features/step_definitions/teacher_grade_assignment.rb:15:in `/^the assignment has a grade$/'
      features/teacher_can_grade_assignment.feature:11:in `Then the assignment has a grade'

Failing Scenarios:
cucumber features/teacher_can_grade_assignment.feature:7 # Scenario: Teacher can grade assignment

teacher_grade_assignment.rb

Given(/^I have a student$/) do
    @teacher = Teacher.new
    @student = Student.new
end

Given(/^They submitted an assignment$/) do
  @teacher.submit_assignment(@student, Assignment.new)
end

When(/^I grade the assignment$/) do
  @teacher.record_grade(@student, 95)
end

Then(/^the assignment has a grade$/) do
    expect(@teacher.assignment_for_student(@student).grade).to eq(95)
end

student_assignment_steps.rb

Given(/^I am a student$/) do
  @student = Student.new #setting as an instance variable to access later on
  @teacher = Teacher.new
end

When(/^I submit an assignment to my teacher$/) do
    @assignment = Assignment.new
    @teacher.submit_assignment(@student, @assignment)
end

Then(/^my teacher should have my assignment$/) do
    expect(@teacher.assignment_for_student(@student)).to eq(@assignment)
end

teacher.rb

class Teacher 
    def initialize
        @assignments = {}
    end

    def record_grade(student, grade)
        assignment = @assignments[student] #assignment equal to assignments of the student
        assignment.grade = grade 
        @assignments[student] = assignment
    end 

    def submit_assignment(student, assignment)
        @assignments[student] = assignment
    end

    def assignment_for_student(student)
        @assignments[student]
    end
end

teacher_spec.rb

require_relative "../lib/teacher"
require "rspec"

describe Teacher do 
    it "should store assignments" do
        student = double
        assignment = double
        subject.submit_assignment(student, assignment)
        expect(subject.assignment_for_student(student)).to eq(assignment)
    end

describe "should record a grade" do 
    it "should record and the grade" do 
        student = double
        assignment = double
        expect(assignment).to receive(:grade=).with(95)
        subject.submit_assignment(student, assignment)
        subject.record_grade(student, 95)
    end
end
end

assignment_spec.rb

require_relative "../lib/assignment"

describe Assignment do 
    it "should store a grade" do 
        subject.grade = 60
        expect(subject.grade).to eq(60)
    end 
end 

assignment.rb

class Assignment
    attr_accessor :grade
end

student.rb

class Student
end

teacher_can_grade_assignment.feature

Feature: Teacher can grade assignment

    As a Teacher
    I can grade my students' assignments
    So that they can know their knowledge level

    Scenario: Teacher can grade assignment
        Given I have a student
        And They submitted an assignment
        When They submitted an assignment
        Then the assignment has a grade

Your assignment has no grade because the teacher never graded it: your feature doesn't call the "I grade the assignment step"