theft

I woke up this morning and as usual checked my email and found that the head of my department in the school had emailed me and informed me that the students in one of my classes had shared the answers.I can see it from two sides. One they cheated. To they pooled their resources and studied together. Now on the one hand it annoys me very much as I hate cheaters but on the other it isnt as if the exam was multiple choice. It was essay and short answer. I feel like lowering everyones score but then I think they did in fact memorize all the required information so they should get the points right. But is memorization enough? Did they learn anything and is it my job to care? I think I will just leave their grades where they stand and be a super pain in the ass next term when I am their writing teacher. Just another adventure in the life of a teacher.