No, I was in my twenties. The process started when I was studying abroad and living in a residence (AmE: dorm), and living with a bunch of people none of whom I had known beforehand probably played a huge role (though the process I described in the grandparent took a couple years to complete, by which time I had been back in my country for about a year, and been reading LW for about half a year). (The experience of no longer wanting to be a reclusive geek and starting to want to have a social life did happen when in high school and only took a few months, but it's not like I tried to be as popular as possible: not being in the bottom decile kind of sufficed.)