What type of i.d. is required to get Apple Education discount?

I want to purchase an iMac and hopefully get the teacher/education discount. I am a retired teacher and have just started the process that will enable me to teach occasionally as a substitute teacher in California. I am wondering if I will be allowed to get the teacher discount. On their website Apple specifically says that one does not have to be a teacher to get the education discount. This is not verbatim, but it sounds as if you are somehow attached to a school in some way (it doesn't specify how - volunteer, janitor, yard duty, etc.) that you are entitled to the discount. I read that the person trying to get the discount must provide an I.D. of some sort (it did not specify)to prove (I suppose) you are indeed involved in Education somehow. Although it also said that teachers, including home school teachers and students in college may use the discount. So does that mean teachers who teach online, etc. do not qualify? I am wondering what type of I.D. Apple requires and are retired teachers, who are only going to be teaching occasionally, given the teacher's discount. I tried 'Chat' to no avail and I tired of waiting on the phone to be connected with someone. I must have called at a high call time. Thanks for any advice/help you can provide!