Teen sensation Hilary A. Duff and her sister Haylie K. Duff are taking classes at Harvard this semester, but you won’t see them around campus anytime soon.

The actors-turned-singers are currently enrolled in the Harvard Extension School and began their classes on Jan. 31 through the Distance Learning Program—all while sitting at home in Los Angeles.

After wrapping up her concert tour in Canada, Hilary Duff expressed excitement about her Harvard education in an online diary last week.

“I’m taking on-line classes for Harvard University. Really cool! I am really excited about going back to school and the on-line classes are really cool!” she wrote in an entry on Feb. 4.

Professors at the Extension School film their lectures, which the sisters will be able to watch online. Other course materials are also available on the web, and all work is submitted and graded by e-mail. Exams may be administered online or in a proctored setting, according to the Extension School website.

“I just started my first day of college on Monday,” Hilary Duff wrote in the online diary entry. “I can watch [the professors] teach, and [I can] take notes from my computer.”

According to their publicist, each sister is taking two classes for credit while continuing to keep up with their packed schedules. Haylie Duff is currently working on the CBS show, “Joan of Arcadia,” and Hilary Duff is about to start production on her next movie, their publicist said.

Yet, if the girls continue in higher education, the courses will only count for credit at the discretion of their future colleges, according to Extension School spokeswoman Linda Cross.

Cross said that while some students in the Distance Learning Program choose to attain degrees by attending additional classes on campus, no official Harvard degree programs are offered online.

According to its website, the Extension School has an “open enrollment” policy—which means anyone who is willing to pay tuition can take classes. Tuition then depends on the course and whether it will be taken for credit. The costs range from $500 for a non-credit history class to $2,000 for more advanced graduate classes.

The selection of online courses offered for the spring semester includes “Investigatory Journalism,” “Theories of Citizenship,” and “Internet and Society: Technologies and the Politics of Control.”

Hilary Duff was the star of “The Lizzie Maguire Show,” and such movies as A Cinderella Story and Cheaper by the Dozen. She also released the hit album Metamorphosis with singles “So Yesterday” and “Come Clean.” Haylie Duff starred in this summer’s cult hit Napoleon Dynamite.