Students who flunked their high school final exams in August sat for a second round on Friday, with officials calling the tests nearly free of fraud.
Students, however, reported cheating was still occurring.
Education Secretary of State Kea Sahorn said there were no reports of problems during the first of the two-day exam period.
Of 21,000 students who took high school exams in August 9,000 failed, Kea Sahorn said, adding that all were registered to retake tests Friday and today.
Deputy Chief of Municipal Police Kong Saran said he did not expect any problems during this round of exams because there are fewer students sitting them and only four test centers in Phnom Penh.
In past years students threw questions out of windows where friends took down answers, wrapped them around rocks and tossed them back. Some teachers also sold copies of exams.
To cut down on fraud this year, the government banned photocopy shops from operating near test centers to prevent reproduction of exam papers or answers.
A change in the test format was also introduced. Rather than having questions on the blackboard, students were given papers with questions written on them. No other papers are allowed inside.
Kong Saran and students interviewed outside two Phnom Penh schools on Friday said no rock throwing was witnessed.
But students said there still was cheating. Hak Sinith, who took the exam at a Don Penh district-testing center, said he had seen some take notes into the exams. He also reported overhearing students collecting bribe money.
“I hope to pass,” said Hak Sinith, a student at Aknuwat High School in Chamkarmon district.
“I want to continue to study at the university but the exam is very hard and I heard that the bribe for a place is very high.”