diff --git a/app/models/school.rb b/app/models/school.rb
index da12d5e6..c883706c 100644
--- a/app/models/school.rb
+++ b/app/models/school.rb
@@ -21,6 +21,6 @@ class School < ApplicationRecord
   end
 
   def grades(academic_year:)
-    Respondent.find_by(school: self, academic_year:)&.enrollment_by_grade&.keys || (-1..12).to_a
+    @grades ||= Respondent.find_by(school: self, academic_year:)&.enrollment_by_grade&.keys || (-1..12).to_a
   end
 end