Never Been Kissed (1999) on Netflix

Josie Geller, at 25 the youngest Chicago Sun-Times copy editor, really is good at her job, which requires brain more than writing skills. The owner of the paper now wants her and no other to report undercover about today's high schools. Josie enrolls and quickly falls back into her own school habits: She was then known as Josie Grossie, she did not make any friends, she even was humiliated. Now, with a good job in her life and with her experiences from a life after school, she tries to fit in as well as possible. Having to seek friendship with some pretty but not very bright girls instead of with the people who really interest her gets really hard for Josie, but her job is at stake, if there is no gripping cover story soon. Falling for a teacher whom she is ordered to shred to pieces in her article, Josie is confronted with her greatest conflict - but also with the chance to undo mistakes she did in her own school days.