She is the youngest graduate in the college's history, said Beth Stull, college spokeswoman.
Despite her age, grades and the fact that she scored 1300 on the Scholastic Aptitude Test at age 13, she doesn't want to be labeled as having high intelligence, she said.
"It is not like I am really smart or anything," she said.
Instead, she said, she just strives to do her best and, if that means being the youngest student in college classes, so be it.
"I base my life on striving to do God's will and to please him. That is the most important thing - to use what he has given me," she said.
She might have graduated at an even younger age except that she agreed to her parents' suggestion that she not take too many classes at once, Keely said.
While Keely was accepted to start taking classes at Hood College in Frederick, Md., in the spring, she has decided instead to take a break, she said. A break, in her case, means she is only taking two classes at HCC this semester.
She plans to major in math, with a minor in French, when she starts at Hood in the fall, she said. She is considering becoming a math professor.
Keely is the daughter of Bill and Jeannie Keely, both of whom have degrees in math.
Jeannie does most of the teaching of Keely and her three younger sisters. Sarah Keely has tutors for French and piano.
While her parents graduated from South Hagerstown High School, the family took Keely out of the public school system after about one year.
It was a good move, family members said Sunday, because Keely was learning at a different speed and age than other students.
"The best thing with home schooling is that I was able to learn at my own pace and I was able to pursue the subjects that I enjoy," she said. "I wasn't held back or pushed forward."
In 2000, at age 13, she started classes at HCC, which is less than a five-minute drive from their house.
She took some of her classes, including biology, with her sister, Colleen, 14, also in attendance.
When Sarah Keely raised her hand in response to a question, biology instructor Rosemary Nickerson said she knew she was about to hear the correct answer.
"She is phenomenal. She scored, consistently, the highest grades," Nickerson said.
Keely said she enjoyed all of her time and classes at the college.
"It has been a really good experience," she said.
Most of the students were not aware of her age, she said.
While some think students who are home-schooled will have trouble socializing later in life, she argues the opposite is true: She learned to talk to people of different ages, she said.
"That helped at HCC, where nobody was my age," she said.
Keely's hobbies including playing the piano and learning the Bible. She has been in national competitions on geography and the Bible.
While continuing to improve her French, she also is learning how to speak Chinese, she said.
"I think learning is fun," she said.