The most popular guy in my high school was a teacher. All girls loved him. He was witty, but he really made fun of his students and thought most were idiots. I didn't crush on him myself though, but I did crush on an university student who was teaching us debate.
Only a small group of students from different generations attended debate so for a while i fell into this clique with their group where they'd all hang out (few high school seniors and the three university students who were teaching, including him). I was the youngest and proud when they first invited me and my friend to join them for drinks one evening.
Another guy had a crush on me, I had a crush on this dude, and we were talking about many interesting things over drinks. When we were done and went out, the university student said he'd drop me and my friend home cause he had a car. For a moment the two of us were alone outside waiting for the others to come, looking at each others eyes, and then he just said "you're 15." Twice.
They dropped us home nicely and nothing happened, but i thought if I had enough time with him and proved my maturity, i could turn things around.
Then the other guy told me he was in love with me, I told him I was in love with someone else, and this was the beginning of the end since I was new in the group and he was everyone's friend.
I remained in love for about a year although I had no contact with the debate teacher, he was the first guy I ever felt anything resembling a crush for. Then I decided enough time has passed and I can rejoin the debate team, so anxious to see him. I came to sign up and he looked at me like i was a stranger and asked stupid questions about the spelling of my name which for some reason deeply hurt me and I took as the ultimate rejection.
Years later I was 19 and talking to a guy from my language group (extracurricular) who was 29, and for some weird reason this past guy came up and i realized whom he was talking about so I told him about my past crush, it was funny. He told me the guy was gay. That was fine, and I found this 29 year old guy to be very interesting in general so now that we were talking about stuff with each other directly for the first time I started feeling attracted to him. The rest of the group had their conversations and we got into our own things and had a good time. I thought that maybe he is starting to like me a bit too. After a short silence, he said to himself "You're a teenager". I reminded him I was 19, so it was pretty irrelevant, to which he said "still a teenager. Wow, I never had a long conversation with an actual teenager."* Nothing ever happened.
*Now that I wrote it down it seems like he is insluting me for being childish, but that's not how it was int he context. I am not sure of the exact phrase, but it was more that he was actually fascinated because despite knowing my age, the awareness just hit him that he got into a deeper conversation with a "technical" teenager and that was weird. I understand that because it happens to me too with no attraction factor attached, that you can regard someone as your equal when you are put in the same context, and then it hits you that they are still what you'd consider a kid if you just thought of their age first. Anyway, it wasn't a mean comment.