The Anti-Corruption Unit (ACU) has called for volunteers to monitor the upcoming national Grade-12 exam for the fourth year in a row in a continued bid to curb once-rampant cheating and corruption during the high-stakes exam.

The ACU on Monday started accepting applications from civil society, associations and individuals who wish to help monitor the exam, which is scheduled to take place on August 21, according to a statement.

However, the number of volunteers needed was not specified, nor was the deadline for applying.

ACU President Om Yentieng referred questions to an official, who could not be reached.

According to the statement, volunteers must own their own vehicles, must avoid conflicts of interest with students taking the exam and must follow the regulations of the ACU and the Ministry of Education.

In 2014, unprecedented government action to crack down on widespread cheating and corruption during the exam saw passage rates plummet from 87 percent in 2013, to just over 25 percent in 2014.

The passage rate rose the following year to nearly 56 percent, and then to 62 percent in 2016.