diff --git a/app/channels/la_exercises_channel.rb b/app/channels/la_exercises_channel.rb
index 278dac36..163e9f11 100644
--- a/app/channels/la_exercises_channel.rb
+++ b/app/channels/la_exercises_channel.rb
@@ -2,7 +2,10 @@
 
 class LaExercisesChannel < ApplicationCable::Channel
   def subscribed
-    stream_from specific_channel
+    set_and_authorize_exercise
+    set_and_authorize_study_group
+
+    stream_from specific_channel unless subscription_rejected?
   end
 
   def unsubscribed
@@ -12,7 +15,20 @@ class LaExercisesChannel < ApplicationCable::Channel
   private
 
   def specific_channel
-    reject unless StudyGroupPolicy.new(current_user, StudyGroup.find(params[:study_group_id])).stream_la?
-    "la_exercises_#{params[:exercise_id]}_channel_study_group_#{params[:study_group_id]}"
+    "la_exercises_#{@exercise.id}_channel_study_group_#{@study_group.id}"
+  end
+
+  def set_and_authorize_exercise
+    @exercise = Exercise.find(params[:exercise_id])
+    reject unless ExercisePolicy.new(current_user, @exercise).implement?
+  rescue ActiveRecord::RecordNotFound
+    reject
+  end
+
+  def set_and_authorize_study_group
+    @study_group = @exercise.study_groups.find(params[:study_group_id])
+    reject unless StudyGroupPolicy.new(current_user, @study_group).stream_la?
+  rescue ActiveRecord::RecordNotFound
+    reject
   end
 end
diff --git a/app/channels/pg_matching_channel.rb b/app/channels/pg_matching_channel.rb
index ac337ae9..01ffa15f 100644
--- a/app/channels/pg_matching_channel.rb
+++ b/app/channels/pg_matching_channel.rb
@@ -3,7 +3,8 @@
 class PgMatchingChannel < ApplicationCable::Channel
   def subscribed
     set_and_authorize_exercise
-    stream_from specific_channel
+
+    stream_from specific_channel unless subscription_rejected?
   end
 
   def unsubscribed
@@ -13,10 +14,6 @@ class PgMatchingChannel < ApplicationCable::Channel
     stop_all_streams
   end
 
-  def specific_channel
-    "pg_matching_channel_exercise_#{@exercise.id}"
-  end
-
   def waiting_for_match
     @current_waiting_user = PairProgrammingWaitingUser.find_or_initialize_by(user: current_user, exercise: @exercise)
     @current_waiting_user.status_waiting!
@@ -40,8 +37,14 @@ class PgMatchingChannel < ApplicationCable::Channel
     ActionCable.server.broadcast(specific_channel, {action: 'joined_pg', users: pg.users.map(&:to_page_context)})
   end
 
+  def specific_channel
+    "pg_matching_channel_exercise_#{@exercise.id}"
+  end
+
   def set_and_authorize_exercise
     @exercise = Exercise.find(params[:exercise_id])
     reject unless ExercisePolicy.new(current_user, @exercise).implement?
+  rescue ActiveRecord::RecordNotFound
+    reject
   end
 end
diff --git a/app/channels/synchronized_editor_channel.rb b/app/channels/synchronized_editor_channel.rb
index ce28fe24..9c7ccc7e 100644
--- a/app/channels/synchronized_editor_channel.rb
+++ b/app/channels/synchronized_editor_channel.rb
@@ -2,7 +2,10 @@
 
 class SynchronizedEditorChannel < ApplicationCable::Channel
   def subscribed
-    stream_from specific_channel
+    set_and_authorize_exercise
+    authorize_programming_group
+
+    stream_from specific_channel unless subscription_rejected?
 
     # We generate a session_id for the user and send it to the client
     @session_id = SecureRandom.uuid
@@ -28,17 +31,6 @@ class SynchronizedEditorChannel < ApplicationCable::Channel
     ActionCable.server.broadcast(specific_channel, message)
   end
 
-  def specific_channel
-    reject unless ProgrammingGroupPolicy.new(current_user, programming_group).stream_sync_editor?
-    "synchronized_editor_channel_group_#{programming_group.id}"
-  rescue NoMethodError => e
-    Sentry.capture_exception(e, extra: {current_user:, programming_group:, session_id: @session_id, identifier: @identifier})
-  end
-
-  def programming_group
-    current_contributor if current_contributor.programming_group?
-  end
-
   def editor_change(message)
     change = message.deep_symbolize_keys
 
@@ -63,6 +55,16 @@ class SynchronizedEditorChannel < ApplicationCable::Channel
     ActionCable.server.broadcast(specific_channel, message)
   end
 
+  private
+
+  def specific_channel
+    "synchronized_editor_channel_group_#{programming_group.id}"
+  end
+
+  def programming_group
+    current_contributor if current_contributor.programming_group?
+  end
+
   def create_message(action, status)
     {
       action:,
@@ -80,4 +82,15 @@ class SynchronizedEditorChannel < ApplicationCable::Channel
       session_id: @session_id,
     }
   end
+
+  def set_and_authorize_exercise
+    @exercise = Exercise.find(params[:exercise_id])
+    reject unless ExercisePolicy.new(current_user, @exercise).implement?
+  rescue ActiveRecord::RecordNotFound
+    reject
+  end
+
+  def authorize_programming_group
+    reject unless ProgrammingGroupPolicy.new(current_user, programming_group).stream_sync_editor?
+  end
 end