Michael Thai, an American of Vietnamese ancestry, thought his bilingualism in Chinese and English would be a plus when he tried to find a job as an English teacher in Beijing.
But it would have been easier if he was white.
"I was asked to submit a résumé and teach a short demonstration course when I was interviewed for a job at a language training school in Beijing," he said. "But sometimes, for the white- skinned people, they don't even ask for a résumé," Thai said, citing the experiences of friends. "Meanwhile, white females can get paid a lot more than other Asian-looking foreigners."
A surge in the mainland's demand for foreign English teachers over the past decade has opened up opportunities for foreign teachers, but has also offered free rides for many unqualified travellers due to weak supervision. State broadcaster China Central Television said a foreign teacher working in China needed a bachelor's degree and a minimum of two years' teaching experience.
But Thai claimed that some people he knew got through job interviews using a made-up résumé, and that the training school he worked for never did any background checks on him.
Though such practices are not uncommon, alarm was only expressed recently after the exposure of two cases involving foreigners linked to child sex scandals who had been teaching in mainland schools for years.
Official figures say more than 180,000 "cultural and educational foreign professionals" worked on the mainland in 2011, teaching at kindergartens, primary and middle schools, colleges, universities and language training schools.
Mainland regulations say that only specially qualified organisations can hire foreign teachers, who are supposed to go through rigorous background checks before being registered as a "foreign expert" by local authorities and granted a work permit.
But Greg Donohue, an English-as-a-second-language instructor who spent two years teaching on the mainland, blogged on BeijingCream.com  that the system was paperwork-heavy but low on actual verification.
"It took me five months to finally obtain a legit visa at my first school in Henan province," he wrote. "Most of that was spent mailing documents back and forth."
He later found out that doctored copies of his degree certificate had been used by the school to obtain residence permits for at least two other teachers.
Xiong Bingqi , deputy director of the Beijing-based 21st Century Education Research Institute, said there were supervisory loopholes in almost each link of the management chain.
Some unqualified schools employed foreign teachers through education agents to avoid supervision, Xiong said. The agents also gave foreigners made up educational qualifications or teaching experience.
"In many cases, foreigners with only a travel visa become teachers," he said. "And they may leave at any time."
A staff member at an agency in Wuhan said her company usually asked foreigners to take care of their own visas. It could help to register their foreign expert certificates in return for fees. Xiong said such a practice made it difficult to ensure the quality of teaching, let alone track those with criminal records.
"Actually the problem is there is no supervision of the certificate issuing procedure and the administration itself should shoulder some responsibility."
Xia Bing, an official with the State Administration of Foreign Experts Affairs, said: "Foreigners who want to work in China ought to provide proof that they have no criminal record."