I don't know what generation you belong to, but I was still in school when mobile phones that could record video became "good enough" that most of my peers in school had them, today I'm ~33.
Ten years older. I'm from West-Europe and most people only got dumbphones around the time I was 18-19 (~2000 and mostly adults or 17-18 year olds). Phones with cameras became widespread quite a few years later. Even when I got an iPhone in 2009, most people were still using good old dumbphone/feature phone Nokias. After 2009 it changed very quickly. I think that aligns with you being 10 years younger + adoption in the US (assuming that you are in the US) being earlier.
Phones were simply not a factor when I was in high school. If you had to call someone on-the-go, you would use one of the many public phone booths and a pre-charged card (there were always rumors that you could spay them with hairspray to get unlimited credit :D). But that almost never happened, you'd mostly just meet people IRL if you wanted to socialize.
I think where I grew up (Sweden) it started with the Sony Ericsson "Walkman" family of phones that could record 320×240 videos I think or something like that, and I think I was around 15 when they became almost ubiquitous at school, so must have been around 2006/2007.
Yes, but there was no social media, just MSN messenger on your PC at home, and you had to transfer the photos and videos from the SonyEricsson/Nokia phone via USB cable or bluetooth to the PC and then send via MSN, or send directly to a friend in person via Bluetooth or infrared which took super long for a single shitty image.
It's just not comparable to how it is today with phones with HD cameras that are constantly online.
I'm basically the last generation that didn't have this always-online social media in high school, and "going online" was an intentional thing, you logged in to MSN messenger and logged out a bit later. You saw a friend logged in, you said hi, chatted some, then said bye, and you or they logged off.