For me much of my high school memories are meshed together. My parents divorce was ongoing, so I mostly just focused on school. I had to switch schools between middle school/jr. high and high school from private to public school so that meant I had to basically start from scratch with my friend group. I feel like being aroace and not knowing it affected my ability to connect with other people because it seemed like all they were interested in talking about were things I couldn't relate to (relationships, dating..etc), and seemed much less interested in or focused on school. At the time I thought it was just the difference between private and public schools. I tried to make friends (and did end up making some), but it was definitely a challenge (my social anxiety did not help) and so I spent a lot of it alone.
I also lost a childhood friend in the beginning of high school because they drifted apart from me (it had been building for a few years). Years later she told me it was because she was questioning her sexuality and wasn't sure how I would react. That always seemed like a bit of an excuse and REALLY confused me because I like to think of myself as an open and understanding person. This recently came up in therapy, and my therapist pointed out that perhaps it actually does make sense if you think about it in the context of me being aroace and not knowing it. Perhaps, she could pick up on the fact that I wasn't interested in those topics and so then went off to find other people to explore those with. That has been quite the realization for me.