This thread is a couple months old at this point but I figured I’d reply anyway.
Maybe you had a different experience but I experienced this transition in middle/high school in west MI. The first Gen iPhone released in 2007. 3G was widespread and while that might be considered slow these days, it was state of the art speed at the time, so it wasn’t considered “slow and unusable”.
In 2007, kids my age didn’t have much tech beyond an iPod or MP3 player. By 2009, almost everyone had a smartphone. That was a huge leap in internet accessibility.