Only destroy the school if it exists

The previous commit caused of the for education tests to fail as it was trying to destroy a school that didn't exist.

This might have been the cause of the intermittent failures as previously if the school didn't exist (but other data did) it would rollback and restore the other data.

Author: zetter-rpf

lib/tasks/for_education.rake

@@ -38,7 +38,7 @@ namespace :for_education do
       SchoolClass.where(id: [school_class_ids]).destroy_all
 
       # Destroy the school
-      School.find(school_id).destroy
+      School.where(id: school_id).destroy_all
 
       Rails.logger.info 'Done...'
     end