Time is of the essence, and if there's one music superstar who learned that life lesson at a young age, it's Christina Perri. On this week's episode of MTV's "When I Was 17," the singer/songwriter recalls being late all the time for high school, which almost cost the future rock star her diploma.

"I remember when I was 17, I almost didn't graduate because I was late so many days," the "Jar of Hearts" singer recalls. "I had this 1981 baby-blue Monte Carlo ... but it was so old and awful and broke down all the time." Perri's brother Nick admits that his sibling was a fan of the superstar lifestyle early on in her teenage years, saying, "She was all about rock and roll and she wanted a muscle car." However, even behind the wheel of her dream car, Perri couldn't deny the less-than-stellar condition of the ride, which led to a number of tardy school days and eventually a little bit of trouble. "My mom wrote me a note one time for the little attendance nun that said, 'Pardon my daughter's lateness. It's her car, it didn't start this morning,' " she recalls. With her mother's note in hand, the Pennsylvania native took advantage and made 70 photocopies for future use. "I gave it to the attendance nun, like, every day. She's like, 'Can you please get another car?' " By the end of high school, Perri's attendance record had finally caught up with her. "In my senior year, I was late a day too many and then my mom found out about all the notes and she said, 'What do you mean you were late 70 days? I didn't write you 70 notes.' " In the end, Perri escaped the consequences, but it was an extremely close call. "The little attendance nun just kind of erased that last day that I had because I had won her over and they let me graduate, but it was close," she says.

"When I Was 17" — this week featuring ?uestlove, Christina Perri and Vanessa Simmons — airs on Saturday at 11 a.m. ET/PT on MTV.