Gan Xiangwei used to stand guard at Peking University (PKU), one of China's most prestigious institutions, but has now realized his dreams teaching primary school children in Beijing.

During his years as a security guard, Gan used his break time to attend lectures and evening classes, which were specifically for the university's logistics staff.

Though Gan, originally from Suizhou City in Hubei Province, was exhausted due to the heavy workload and shift work, he was grateful for the chance to study.

"I felt like a bird standing guard in PKU and only the sky was the limit," wrote Gan in his autobiography, which was published last year.

After studying Chinese Language and Literature, he graduated in May 2012 and immediately began teaching at Beijing Jianhua Experimental School.

In China, security guards are commonly made up of migrant workers and those that have been laid-off, most of whom are poorly educated or illiterate.

There are many security guards like Gan, who did not have the chance to study at school but take the opportunity later in life.

According to a report from the Ministry of Public Security in 2011, there are more than four million registered security guards in China.

Gan is not the only guard at the university to clinch a seat in the classroom.

Zhang Guoqiang, vice captain of the security team of PKU, now holds several diplomas and a certificate to practice law. "My dream to go to PKU was rekindled when I came here in 1994, and I decided to seize the opportunity," Zhang said.

Coming from a rural village in central China's Henan Province, the farmer-turned guard said he hopes to encourage more young people to realize their dreams.

Standing guard first and becoming a university student is a bit of a tradition. According to Yanzhao Metropolis Daily, some 500 PKU security guards have enrolled at undergraduate and postgraduate schools over the last 20 years.

For young Chinese people, the stories of PKU security guards offer them "positive energy".

"Want to become a PKU student? Go there and become a security guard first," said "Aubrey" on his Sina Weibo, China's twitter-like microblogging service.

Professor Bao Wei with the Graduate School of PKU teaches evening classes at the university. She said migrant-worker students displayed a vigorous thirst for knowledge.

"Education should give more opportunities to each and every youngster to live their dreams, and I'm proud to give them instructions to rekindle their dreams," said Bao.

Related:

First-tier cities barely livable, report says

Graduate-turned-butcher shares experience with alma mater