The strangest thing to think about is how little I was aware of most people, in all their depth and complexities, when I was in high school. Meaning that I only ever considered them from their surface layers, that I only ever thought of them in the vaguest of ways, and I never thought to go much deeper. Some of them I had known (though not particularly well) since third grade, so maybe it was a process of desensitization. Just the years turning over and over and bringing little change, so some classmates just became familiar faces my mind never registered.
Sometimes when I'm bored or procrastinating, I look at the profiles of people I'd once shared the same classrooms with or walked down the same hallways, and there's always the slightly unsettling feeling that I had never known them at all.