My first day of high school was....entertaining.
I remember pulling up to school in my best friend's redish-orange BMW. She was 16, I was 14. We hit the curb, everyone looked, we bounced, and then slowly moved into a parking space. A bit embarrassing, but nothing someone couldn't forget by 1st period.
Other than that, high school was a pretty big blurr. Yeah, I've got particular moments that I recall, but overall it came and went without too much of a hassle. I mean, I did have a kid my junior year, but ya know, that was just another "curb" to get over and we all did. :)
My advice to teenager in high school: enjoy it, put forth the effort for it will pay off, dream big, and laugh hard. :)