Do you remember your first erection? If not, the earliest one?

I was in 6th grade. In my school uniforms were obligatory. Girls needed to wear skirts, long white socks, and black leather school shoes
The class was sitting in chairs, chairs on one side of the wall, and more chairs against the other side.
A white girl with thick legs was sitting in front of me; suddenly she opens her legs and I can see her undies. Her underwear was white with flowers printed all over, pic related.
My dick went rock hard when I watched that, I was just staring at her panties for like the whole fucking class and she wouldn't even notice it, she was busy talking to the other girls at her side.
I even remember thinking shit like: "wow that's fucking hot", "why is my penis so rock hard?", "why do I feel funny for this?" "what's happening? why do I feel like this?"