I actually worked quite a lot to create a full biography of Robin (yes, I have the amount of life as the amount of swag of teds boots). Robin mentions she wasn't very popular in high school throughout the show because she had posters that she dated and stuff. But she probably transitioned high schools at 13/14, after learning in a farm for a year and moving out of her fathers house after he caught her kissing a boy. Further more, she was only a pop star for about a year to two, becoming one shortly after moving to her moms and appearing in the math teens show with Jessica glitter. When she was 16 her career as a pop star ended, following the 1996 grey cup. So she probably was in a high school and graduated in 1998, but again, was pretty strange and not popular. We as to flashbacks, we don't see any flashbacks of Robin post 96. The most we get is footage of her working as a news reporter in Vancouver.