diff --git a/app/controllers/reports_controller.rb b/app/controllers/reports_controller.rb
new file mode 100644
index 000000000..9f94af676
--- /dev/null
+++ b/app/controllers/reports_controller.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+class ReportsController < ApplicationController
+  REPORT_CLASSES = {
+    'basic' => Reports::BasicReport,
+    'review_response_map' => Reports::ReviewReport
+  }.freeze
+
+  before_action :set_assignment
+  before_action :authorize
+
+  # Only teaching staff (instructor or TA) of the specific assignment may view reports.
+  def action_allowed?
+    current_user_teaching_staff_of_assignment?(@assignment.id)
+  end
+
+  # POST /reports/fetch_report
+  # Returns the requested report as JSON.
+  def fetch_report
+    type = params[:type] || 'basic'
+
+    report_class = REPORT_CLASSES[type]
+    unless report_class
+      return render json: {
+        error: "Unknown report type: #{type}. Valid types: #{REPORT_CLASSES.keys.join(', ')}"
+      }, status: :unprocessable_entity
+    end
+
+    data = report_class.for_assignment(@assignment).run
+    render json: { type: type, assignment_id: @assignment.id }.merge(data)
+  rescue StandardError => e
+    render json: { error: e.message }, status: :internal_server_error
+  end
+
+  private
+
+  def set_assignment
+    @assignment = Assignment.find(params[:assignment_id])
+  rescue ActiveRecord::RecordNotFound
+    render json: { error: 'Assignment not found' }, status: :not_found
+  end
+end
diff --git a/app/models/Item.rb b/app/models/Item.rb
index 0b6535228..807bcf06a 100644
--- a/app/models/Item.rb
+++ b/app/models/Item.rb
@@ -5,7 +5,7 @@ class Item < ApplicationRecord
   belongs_to :questionnaire # each item belongs to a specific questionnaire
   has_many :answers, dependent: :destroy, foreign_key: 'item_id'
   attr_accessor :choice_strategy
-  
+
   validates :seq, presence: true, numericality: true # sequence must be numeric
   validates :txt, length: { minimum: 0, allow_nil: false, message: "can't be nil" } # text content must be provided
   validates :question_type, presence: true # user must define the item type
diff --git a/app/models/reports/base_reducer.rb b/app/models/reports/base_reducer.rb
new file mode 100644
index 000000000..e9eb34475
--- /dev/null
+++ b/app/models/reports/base_reducer.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+module Reports
+  # Base class for streaming reducers.
+  #
+  # Design rationale (addresses two anti-patterns from the naive approach):
+  #
+  #   Anti-pattern 1 — "fetch_responses": loading all records into an unnamed
+  #   ad-hoc array before processing wastes memory and forces the entire result
+  #   set into Ruby-land. Instead, #run streams the source relation via
+  #   find_each so memory usage scales with the number of *groups*, not rows.
+  #
+  #   Anti-pattern 2 — "default metrics in base": encoding avg_score or any
+  #   domain metric in the base class ties every reducer to one shape of math.
+  #   This class contains *only* the reducer scaffold; each subclass owns its
+  #   accumulate/finalize logic entirely.
+  #
+  # Subclasses must implement (private):
+  #   source                 → AR relation (consumed via find_each)
+  #   initial_state          → empty accumulator value
+  #   accumulate(state, row) → mutates state in place; all grouping and domain
+  #                            math lives here, not in the base class.
+  #
+  # Subclasses may override (private):
+  #   finalize(state) → transforms finished state into the output hash
+  #                     (default: returns state unchanged)
+  class BaseReducer
+    # Factory method for assignment-scoped reports.
+    def self.for_assignment(assignment)
+      new(assignment)
+    end
+
+    # Factory method for course-scoped reports.
+    def self.for_course(course)
+      new(course)
+    end
+
+    # @param reportable [Assignment, Course] the object the report is scoped to.
+    # Subclasses reference @reportable instead of a type-specific variable so
+    # the same reducer works for any reportable entity.
+    def initialize(reportable)
+      @reportable = reportable
+    end
+
+    # Runs the reducer: stream → accumulate → finalize.
+    #
+    # Accepts an optional shared_state so that multiple reducers can write
+    # into the same hash without a merge loop. When shared_state is provided,
+    # initial_state is ignored — the coordinator owns state initialization.
+    # finalize is always called, even when shared_state is provided.
+    #
+    # Benefits of this structure over writing reducer code directly:
+    #   1. Memory safety — find_each streams in batches of 500 rather than
+    #      loading the entire relation into Ruby. Every report gets this for free.
+    #   2. New reports are just data — subclasses define source/initial_state/
+    #      accumulate/finalize; the reducer wiring is not their concern.
+    #   3. Single place for cross-cutting concerns — logging, timing, or error
+    #      handling can be added here once and applies to every report.
+    def run(shared_state = nil)
+      state = shared_state || initial_state
+      source.find_each(batch_size: 500) do |row|
+        accumulate(state, row)
+      end
+      finalize(state)
+    end
+
+    private
+
+    def source        = raise NotImplementedError, "#{self.class}#source"
+    def initial_state = raise NotImplementedError, "#{self.class}#initial_state"
+
+    def accumulate(_state, _row)
+      raise NotImplementedError, "#{self.class}#accumulate"
+    end
+
+    def finalize(state) = state
+  end
+end
\ No newline at end of file
diff --git a/app/models/reports/basic_report.rb b/app/models/reports/basic_report.rb
new file mode 100644
index 000000000..a1b5ac614
--- /dev/null
+++ b/app/models/reports/basic_report.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Reports
+  # Basic report: minimal reportable metadata.
+  # Used as a fallback when no specific report type is requested.
+  # No streaming needed — all data comes from the already-loaded reportable.
+  class BasicReport
+    # Factory method for assignment-scoped reports.
+    def self.for_assignment(assignment)
+      new(assignment)
+    end
+
+    # Factory method for course-scoped reports.
+    def self.for_course(course)
+      new(course)
+    end
+
+    # @param reportable [Assignment, Course] the object the report is scoped to.
+    def initialize(reportable)
+      @reportable = reportable
+    end
+
+  def run
+    {
+      reportable: {
+        id:                      @reportable.id,
+        name:                    @reportable.name,
+        num_review_rounds:       @reportable.num_review_rounds,
+        varying_rubrics_by_round: @reportable.varying_rubrics_by_round?
+      }
+    }
+  end
+end
+end
diff --git a/app/models/reports/review_report.rb b/app/models/reports/review_report.rb
new file mode 100644
index 000000000..f97b98512
--- /dev/null
+++ b/app/models/reports/review_report.rb
@@ -0,0 +1,160 @@
+# frozen_string_literal: true
+
+module Reports
+  # Peer-review report: returns raw review rows (reviewer, reviewee, responses,
+  # scores) plus computed score percentages per reviewer and per-team averages.
+  #
+  # Three data sources:
+  #
+  #   Review rows — loads all ReviewResponseMaps for the assignment with reviewer,
+  #     reviewee, responses, and scores eagerly loaded, then serializes via as_json.
+  #
+  #   ScoresReducer — streams ReviewResponseMap rows for the assignment. For each
+  #     map, picks the latest submitted response per round (via
+  #     latest_submitted_response_by_round) and computes a score percentage from
+  #     the response's answers relative to the questionnaire's max score.
+  #     Output: { reviewer_id => { reviewee_id => { round => score_pct } } }
+  #
+  #   AvgRangesReducer — streams AssignmentTeam rows. For each team, the average
+  #     review score is computed from its eagerly-loaded review_mappings and their
+  #     nested responses and scores (via aggregate_review_grade).
+  #     Output: { team_id => avg_score }
+  #
+  # Output:
+  #   {
+  #     reviews: [
+  #       {
+  #         id: Integer,                         # ReviewResponseMap id
+  #         reviewer: {
+  #           id: Integer,                       # AssignmentParticipant id
+  #           user: { id: Integer, name: String }
+  #         },
+  #         reviewee: { id: Integer },           # AssignmentTeam id
+  #         responses: [
+  #           {
+  #             id: Integer,
+  #             round: Integer,                  # review round number (1-based)
+  #             is_submitted: Boolean,
+  #             additional_comment: String,
+  #             scores: [
+  #               {
+  #                 id: Integer,
+  #                 answer: Integer,             # raw score value
+  #                 comments: String,
+  #                 item: { id: Integer, txt: String, weight: Integer }
+  #               }
+  #             ]
+  #           }
+  #         ]
+  #       }
+  #     ],
+  #     reviewer_scores: {
+  #       reviewer_id => {
+  #         reviewee_id => {
+  #           round => Float   # score as a percentage (0–100)
+  #         }
+  #       }
+  #     },
+  #     team_averages: {
+  #       team_id => Float     # average review score across all reviewers, as a percentage (0–100)
+  #     }
+  #   }
+  class ReviewReport
+    # Whitelist for as_json — includes only fields the frontend needs,
+    # excluding internal columns (raw FKs, timestamps, STI type, etc.).
+    MAP_JSON_OPTIONS = {
+      only: [:id],
+      include: {
+        reviewer: {
+          only: [:id],
+          include: { user: { only: %i[id name] } }
+        },
+        reviewee: {
+          only: [:id],
+          include: { user: { only: %i[id name] } }
+        },
+        responses: {
+          only: %i[id round additional_comment is_submitted],
+          include: {
+            scores: {
+              only: %i[id answer comments],
+              include: { item: { only: %i[id txt weight] } }
+            }
+          }
+        }
+      }
+    }.freeze
+
+    def self.for_assignment(assignment)
+      new(assignment)
+    end
+
+    def initialize(reportable)
+      @reportable = reportable
+    end
+
+    def run
+      maps = ReviewResponseMap
+               .for_assignment(@reportable.id)
+               .includes(reviewer: :user, reviewee: :user, responses: { scores: :item })
+
+      {
+        reviews:          maps.as_json(MAP_JSON_OPTIONS),
+        reviewer_scores:  ScoresReducer.new(@reportable).run,
+        team_averages:    AvgRangesReducer.new(@reportable).run
+      }
+    end
+
+    # -----------------------------------------------------------------------
+    # Reducer 1 — per-reviewer × reviewee × round score percentages.
+    # Streams ReviewResponseMap rows with responses and scores eagerly loaded.
+    # For each map, delegates to latest_submitted_response_by_round to pick
+    # the most recent submitted response per round without N+1 queries.
+    # Output: { reviewer_id => { reviewee_id => { round => score_pct } } }
+    # -----------------------------------------------------------------------
+    class ScoresReducer < BaseReducer
+      def source
+        ReviewResponseMap
+          .for_assignment(@reportable.id)
+          .includes(responses: { scores: :item })
+      end
+
+      def initial_state
+        Hash.new do |state, reviewer_id|
+          state[reviewer_id] = Hash.new { |by_reviewee, reviewee_id| by_reviewee[reviewee_id] = {} }
+        end
+      end
+
+      def accumulate(state, map)
+        map.latest_submitted_response_by_round.each do |round, response|
+          next if response.maximum_score.zero?
+
+          score_pct = (response.aggregate_questionnaire_score.to_f / response.maximum_score * 100).round(2)
+          state[map.reviewer_id][map.reviewee_id][round] = score_pct
+        end
+      end
+    end
+
+    # -----------------------------------------------------------------------
+    # Reducer 2 — per-team average review score.
+    # Streams AssignmentTeam rows with review_mappings, responses, and scores
+    # eagerly loaded to avoid N+1. Delegates score computation to
+    # aggregate_review_grade which picks the latest submitted response per
+    # round per map and normalizes the score.
+    # Output: { team_id => avg_score }
+    # -----------------------------------------------------------------------
+    class AvgRangesReducer < BaseReducer
+      def source
+        AssignmentTeam
+          .where(parent_id: @reportable.id)
+          .includes(review_mappings: { responses: { scores: :item } })
+      end
+
+      def initial_state = {}
+
+      def accumulate(state, team)
+        state[team.id] = team.aggregate_review_grade
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/app/models/response.rb b/app/models/response.rb
index c6233dabe..e8ed2d7ba 100644
--- a/app/models/response.rb
+++ b/app/models/response.rb
@@ -88,7 +88,7 @@ def aggregate_questionnaire_score
     sum = 0
     scores.each do |s|
       # For quiz responses, the weights will be 1 or 0, depending on if correct
-      sum += s.answer * s.item.weight unless s.answer.nil?  #|| !s.item.scorable?
+      sum += s.answer * s.item.weight unless s.answer.nil? #|| !s.item.scorable?
     end
     # puts "sum: #{sum}"
     sum
diff --git a/app/models/response_map.rb b/app/models/response_map.rb
index bac967bfb..4fb0e6df8 100644
--- a/app/models/response_map.rb
+++ b/app/models/response_map.rb
@@ -8,6 +8,16 @@ class ResponseMap < ApplicationRecord
 
   alias map_id id
 
+  # Returns the latest submitted response per round for this map.
+  # Relies on responses being eager-loaded (e.g. via includes) to avoid N+1.
+  # Output: { round => response }
+  def latest_submitted_response_by_round
+    responses
+      .select(&:is_submitted)
+      .group_by(&:round)
+      .transform_values { |rs| rs.max_by(&:id) }
+  end
+
   # Shared helper for Response#rubric_label; looks up the declarative constant so each map advertises its UI label
   def response_map_label
     const_name = "#{self.class.name.demodulize.underscore.upcase}_TITLE"
diff --git a/app/models/review_response_map.rb b/app/models/review_response_map.rb
index e339e1b62..0a8e02697 100644
--- a/app/models/review_response_map.rb
+++ b/app/models/review_response_map.rb
@@ -3,6 +3,8 @@ class ReviewResponseMap < ResponseMap
   include ExpertizaConstants::ResponseMapTitles
   belongs_to :reviewee, class_name: 'Team', foreign_key: 'reviewee_id', inverse_of: false
 
+  scope :for_assignment, ->(assignment_id) { where(reviewed_object_id: assignment_id) }
+
   # Returns the assignment associated with this review map.
   def reviewer_assignment
     return assignment
diff --git a/config/routes.rb b/config/routes.rb
index 47da3d9e0..f8ee581b4 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -194,6 +194,12 @@
           delete :delete_participants
         end
       end
+      resources :reports, only: [] do
+        collection do
+          post :fetch_report
+        end
+      end
+
       resources :grades do
         collection do
           get '/:assignment_id/view_all_scores', to: 'grades#view_all_scores'