In case you haven't picked up on this yet, I'm a teacher. I teach English to high school students who, generally, already know a bunch of English. I thought this would be a plus and would give me ample free time to pursue my real passion, English. I have been in the game professionally for almost 20 years and have, over that time, taught (well...stood in the front of the room and tried to amuse) close to 2000 students. That isn't an exact number as I have had some students in more than one class, and there was a range of class size and number of classes taught each year, but it is not far off. Also, with my work in administration, and on clubs and publications, I met with and worked with hundreds more, to varying degrees.
I say this all in my own defense.
Over the last 19 years, I have run in to former students in a variety of different contexts. Occasionally (I can think of 3 cases in particular) I completely blanked on who the former student was. In one case, I guessed his name after he gave me a hint, in another, I was befuddled until he told me and in a third, I asked a mutual friend to remind me of the name. Now, once I get the name and can open up the dusty filing cabinet that is my memory, and find the right file, I'm usually OK, but I feel bad that I forget students. For the most part, though, if you had me or worked with me, or I had any reason to deal with you, I'll recognize you. You might have to remind me of your name, but once that sinks in, I will probably be able to tell you all sorts of embarrassing stories about yourself that you have been trying to forget. I will tell you if you still owe me any work, and whether you were a "good" kid or not. Hint -- meh. I still have my yearbooks and my grade books so I will run home and relive my memories of you. My students really do define my world and each one is important changed me. Realize that while I'm slow on the uptake, you do have a permanent place somewhere in my thoughts.
And most of the time, if I see you in a social setting (an event, shopping, the Jumbotron), I won't say anything, but I'll recognize you. While it would be nice to think that you recognize and remember me and that when you sit around with your friends, all in your early-midlife crises, musing about the greatest teacher ever you all say my name as one voice, and then there is a solemn silence and you raise your glasses and toast to me, the greatest teacher EVER, I doubt you do that. You should, but I doubt you do. So I won't make it awkward by coming over and assuming that you have built a shrine to me and have been looking forward to this meeting so you can tell me how you named all your children after me.
You had many teachers before me, and a whole bunch after. And while I think I made you what you are today (if it is a good thing...if you are a murderer, I blame the entire math department) I can understand why, when we meet 10 years after your final exam in my class, you can't remember my name or how you know me. I have had that happen and, while it hurts, I understand it. Just remember what I said on the first day of class (and I say this to every class, every year), I am not good with names and faces so give me time. But remember -- I do know you. You are important. And I'll never say if you were or weren't my favorite student.