More than 500 security guards working at Peking University (PKU) have sat for examinations in pursuit of a better education and life over the past 20 years. Some have even acquired master's degrees and become university professors.

According to Wang Guiming, head of security at the university, most of the 500 guards currently working on campus hold associate degrees. Some of them have graduated from universities, and 12 even hold master's degrees.

Zhang Juncheng, who used to be a security guard at PKU, was admitted to the university's law school after independently studying for the necessary examinations in 1995. Now he is principal of a vocational school in Changzhi, Shanxi province, and he plans to build the first private college in Changzhi within 10 years.

Another example is Gan Xiangwei, a security guard at the university who was raised in rural Hubei province. He came to PKU to work in 2007. A year later, he began studying at the university's Department of Chinese Language and Literature. He is now a published author and a frequent public speaker.

There is a joke that every security guard is really a philosopher because they constantly ask people about their identities, origins and destinations. Yet behind that joke lies a stark contrast between the guards' lack of formal education and their high intelligence. The successes of PKU's former security guards has contributed immeasurably to subverting harmful prejudices.