diff --git a/spec/controllers/exercises_controller_spec.rb b/spec/controllers/exercises_controller_spec.rb
index 555cf093f..51209b3ab 100644
--- a/spec/controllers/exercises_controller_spec.rb
+++ b/spec/controllers/exercises_controller_spec.rb
@@ -202,7 +202,7 @@
 
     context 'with other users accessing an unpublished exercise' do
       let(:exercise) { create(:fibonacci, unpublished: true) }
-      let(:user) { create(:teacher) }
+      let(:user) { create(:external_teacher) }
 
       before { perform_request.call }
 
@@ -442,7 +442,8 @@
     end
 
     context 'when the user cannot update the exercise' do
-      let(:codeharbor_link) { create(:codeharbor_link, api_key: 'anotherkey') }
+      let(:user) { create(:external_teacher) }
+      let(:codeharbor_link) { create(:codeharbor_link, user:, api_key: 'anotherkey') }
 
       it 'renders correct response' do
         post_request
diff --git a/spec/factories/internal_user.rb b/spec/factories/internal_user.rb
index c52bf94e6..808ec92c1 100644
--- a/spec/factories/internal_user.rb
+++ b/spec/factories/internal_user.rb
@@ -27,6 +27,10 @@
     transient do
       teacher_in_study_group { true }
     end
+
+    factory :external_teacher do
+      consumer { association :consumer, name: 'Other Consumer' }
+    end
   end
 
   factory :learner, class: 'InternalUser' do
diff --git a/spec/factories/shared_traits.rb b/spec/factories/shared_traits.rb
index 3f6cbf634..0e6501c86 100644
--- a/spec/factories/shared_traits.rb
+++ b/spec/factories/shared_traits.rb
@@ -23,10 +23,16 @@
 
   trait :member_of_study_group do
     after(:create) do |user, evaluator|
-      # Do not create a study group if already passed
-      if user.study_groups.blank?
-        study_group = create(:study_group)
+      if user.study_groups.blank? && user.is_a?(ExternalUser)
+        # Do not create a study group if already passed
+        study_group = create(:study_group, consumer: user.consumer)
         user.study_groups << study_group
+      elsif user.is_a?(InternalUser)
+        # Always add the user to the default study group
+        default_study_group = user.consumer.study_groups.find_by(external_id: nil)
+        StudyGroupMembership.find_or_create_by!(study_group: default_study_group, user:)
+        # Reload the study groups to ensure the membership is reflected
+        user.study_groups.reload
       end
 
       user.study_group_memberships.update(role: 'teacher') if evaluator.teacher_in_study_group
diff --git a/spec/policies/exercise_policy_spec.rb b/spec/policies/exercise_policy_spec.rb
index bcad83fe4..2c25ffd5f 100644
--- a/spec/policies/exercise_policy_spec.rb
+++ b/spec/policies/exercise_policy_spec.rb
@@ -209,10 +209,18 @@
           expect(policy).to permit(exercise.author, exercise)
         end
 
-        it 'does not grant access to everyone' do
-          %i[external_user teacher].each do |factory_name|
-            expect(policy).not_to permit(create(factory_name), exercise)
-          end
+        it 'grants access to teachers of the same study group' do
+          # By default, the exercise author and the teacher are internal users and share the same study group
+          expect(policy).to permit(create(:teacher), exercise)
+        end
+
+        it 'does not grant access to teachers of another consumer' do
+          # With another consumer, the teacher is in another study group, too.
+          expect(policy).not_to permit(create(:external_teacher), exercise)
+        end
+
+        it 'does not grant access to external users' do
+          expect(policy).not_to permit(create(:external_user), exercise)
         end
       end
     end
@@ -222,7 +230,7 @@
     describe '#resolve' do
       let(:admin) { create(:admin) }
       let(:external_user) { create(:external_user) }
-      let(:teacher) { create(:teacher) }
+      let(:teacher) { create(:external_teacher) }
 
       before do
         [admin, teacher].each do |user|
diff --git a/spec/policies/request_for_comment_policy_spec.rb b/spec/policies/request_for_comment_policy_spec.rb
index 5ec21715b..7c225666e 100644
--- a/spec/policies/request_for_comment_policy_spec.rb
+++ b/spec/policies/request_for_comment_policy_spec.rb
@@ -157,7 +157,7 @@
       end
     end
 
-    let(:rfc_author) { create(:learner, consumer: author_consumer, study_groups: author_study_groups) }
+    let(:rfc_author) { create(:external_user, consumer: author_consumer, study_groups: author_study_groups) }
     let(:author_study_groups) { create_list(:study_group, 1, consumer: author_consumer) }
     let(:rfc) { create(:rfc, user: rfc_author) }
 
diff --git a/spec/services/proforma_service/import_spec.rb b/spec/services/proforma_service/import_spec.rb
index e5239c2da..985ea0e62 100644
--- a/spec/services/proforma_service/import_spec.rb
+++ b/spec/services/proforma_service/import_spec.rb
@@ -182,7 +182,7 @@
       end
 
       context 'when another user imports the exercise' do
-        let(:import_user) { create(:teacher) }
+        let(:import_user) { create(:external_teacher) }
 
         it 'raises a proforma error' do
           expect { imported_exercise.save! }.to raise_error ProformaXML::ExerciseNotOwned
diff --git a/spec/system/authentication_system_spec.rb b/spec/system/authentication_system_spec.rb
index 2ab18c575..fb27e918b 100644
--- a/spec/system/authentication_system_spec.rb
+++ b/spec/system/authentication_system_spec.rb
@@ -3,7 +3,7 @@
 require 'rails_helper'
 
 RSpec.describe 'Authentication' do
-  let(:user) { create(:teacher) }
+  let(:user) { create(:external_teacher) }
   let(:password) { attributes_for(:teacher)[:password] }
 
   context 'when signed out' do