Legal analysis: going through the back door is a bribe. It must be illegal to go to college through the back door. There must be more than one or two people taking bribes. Of course it's illegal.

Legal basis: Article 1 of the Code of Practice for Candidates in the National Entrance Examination for Colleges and Universities in People's Republic of China (PRC) is honest and trustworthy, and consciously abides by the examination discipline, and shall not hinder invigilators and examination staff from performing their duties for any reason, disturb the order of examination rooms and other examination workplaces, or endanger the health and safety of others.