diff --git a/.ruby-version b/.ruby-version
index 9c25013d..47b322c9 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.3.6
+3.4.1
diff --git a/Gemfile.lock b/Gemfile.lock
index 1e91cc17..0df118be 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -204,7 +204,7 @@ GEM
       activerecord (>= 4.0.0)
     globalid (1.2.1)
       activesupport (>= 6.1)
-    google-protobuf (4.28.2-x86_64-linux)
+    google-protobuf (4.28.2)
       bigdecimal
       rake (>= 13)
     guard (2.18.1)
@@ -261,6 +261,7 @@ GEM
     matrix (0.4.2)
     method_source (1.0.0)
     mini_mime (1.1.5)
+    mini_portile2 (2.8.8)
     minitest (5.25.1)
     msgpack (1.7.2)
     multi_json (1.15.0)
@@ -281,7 +282,8 @@ GEM
     newrelic_rpm (9.6.0)
       base64
     nio4r (2.7.3)
-    nokogiri (1.16.7-x86_64-linux)
+    nokogiri (1.16.7)
+      mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
     notiffany (0.1.3)
       nenv (~> 0.1)
@@ -548,7 +550,7 @@ DEPENDENCIES
   watir
 
 RUBY VERSION
-   ruby 3.3.6p108
+   ruby 3.4.1p0
 
 BUNDLED WITH
    2.5.11
diff --git a/app/models/report/survey_item_by_item.rb b/app/models/report/survey_item_by_item.rb
index 84bf5128..caa02385 100644
--- a/app/models/report/survey_item_by_item.rb
+++ b/app/models/report/survey_item_by_item.rb
@@ -61,13 +61,13 @@ module Report
       data << headers
 
       survey_items_by_id = ::SurveyItem.by_id_includes_all
-      academic_years.each do |academic_year|
-        mutex = Thread::Mutex.new
 
-        pool_size = 2
-        jobs = Queue.new
-        schools.each { |school| jobs << school }
+      mutex = Thread::Mutex.new
+      pool_size = 2
+      jobs = Queue.new
+      schools.each { |school| jobs << school }
 
+      academic_years.each do |academic_year|
         workers = pool_size.times.map do
           Thread.new do
             while school = jobs.pop(true)
@@ -108,8 +108,8 @@ module Report
                 row.concat(padding)
 
                 # filter out response rate at subcategory level <24.5% for school average
-                if ::StudentResponseRateCalculator.new(subcategory: survey_item.subcategory, school:,
-                                                       academic_year:).meets_student_threshold?
+                if response_rate(subcategory: survey_item.subcategory, school:,
+                                 academic_year:).meets_student_threshold?
                   row.append("#{survey_item.survey_item_responses.where(
                     # We allow the nil (unknown) grades in the school survey item average
                     # also filter less than 10 responses in the whole school
@@ -154,6 +154,15 @@ module Report
       end
     end
 
+    def self.response_rate(subcategory:, school:, academic_year:)
+      @response_rate ||= Hash.new do |memo, (subcategory, school, academic_year)|
+        memo[[subcategory, school, academic_year]] =
+          ::StudentResponseRateCalculator.new(subcategory:, school:, academic_year:)
+      end
+
+      @response_rate[[subcategory, school, academic_year]]
+    end
+
     def self.write_csv(csv:, filepath:)
       File.write(filepath, csv)
     end