While most people her age are struggling to stay alive, Estelle Rees-Arroyo is struggling to memorize history facts and figures … for her next quiz.

The 90-year-old grandmother is hitting the books again to finally finish her long-delayed bachelor’s degree. She may be the oldest out of 30,000 students at California State University, Sacramento, but she’s certainly one of the most ambitious.

In between classes and her daily 140-mile commute to campus, Estelle told Growing Bolder that she once spent four months in a retirement home and found out that it wasn’t for her.

Find out what it’s like for her to sit through history classes that cover events she remembers experiencing as a young woman and why she had to turn down Ellen DeGeneres.