I was ten, and had dreams about winning the hearts of girls in my class, but having no prior feelings for them prior to or following said dreams. More significant was the feelings I had for this girl I knew, who had a unisex name. I kept mistaking her for the boy with the same name, much to her annoyance. She was quite pretty though so I kept looking at her. She eventually told me to stop looking at her.
The next girl I recall having that sort of attraction to was in the beginning of junior high school. She was quite critical of me, so I knew her from having to fend off her criticisms, but she was also pretty and I couldn't help but look at her. She caught me once and said, "I have a boyfriend, you know." Just a little bit more subtle than the first one. I was quite defensive.
I still didn't want to have anything to do with the opposite sex until I was about fourteen and a half and the idea suddenly dawned on me that many girls were quite attractive, and I should try to go out with them. One in particular I became particularly infatuated with after managing to convince myself that she liked me. She did appear to enjoy my company a bit more than the previous two, but I was still rejected.