I loved high school, so it's hard to pick out any singular favorite moments - I loved getting parfaits and bubble tea with my friends after school, playing capture the flag in PE (I hated PE but I always loved it when we had nothing to do and the teachers just let us play games), slipping "notes" into my friends' lockers/receiving notes in mine even though I see them every day, making a sweater that actually fit me and looked good in sewing class, the magic of watching the photos I took with an actual shoebox develop in photography class, getting praised in electronics class, etc (yes I learned maths and biology too but I have more fond memories of electives than academics, lol).
I'm sure my mind is cherry picking right now and there were lots of bad moments too, but since it's been a few years since graduation I've left (most of) those behind and just remembered the fun times.