Nyaope addiction is wreaking havoc in schools and some principals believe the drug has an impact on the decline in the class of 2014's matric results.

Steven Khanyile, principal at Morris Isaacson Secondary School in Jabavu, Soweto, said the pass rate at the school plummeted from 87% in 2013 to 72%.

He cited nyaope use by pupils as one reason for the decline.

"The community is selling nyaope to learners during school time through the fence. These kids sleep in class and only come to school for the feeding schemes," he said.

Joseph Malindi, principal at Orlando West High School, said they expected bigger problems this year as more pupils from Grade 11 who are known drug addicts have been promoted to Grade 12.

The school, which was named as one of the beneficiaries in former president Nelson Mandela's will, scored a 94% matric pass rate - an increase from 87% in 2013.

But Malindi is concerned that parents will be sending more children to his school as they performed well this year.

"Learners addicted to nyaope will be dumped here, which means more challenges for us," he said.

He said the school was aiming for a 100% pass rate but the nyaope scourge was causing problems.

"One of our bright students, who is a nyaope addict, wrote exams behind bars and passed," he said.

"We are working with Sanco [SA National Civic Organisation] and the SAPS to fight drug usage at the school."

Khanyile said his school planned to implement strict measures to curb drug usage. Searches are to be conducted every morning before pupils enter the school premises.

A recent report by the SA Community Epidemiology Network on Drug Use stated that heroin use among black communities had increased significantly.

The report cited nyaope, which contains heroin, as one of the causes of the increase.

Spokesman for the department of basic education Elijah Mhlanga admitted that drugs were a huge problem in schools.

However, he said it was not easy to say the use of drugs in schools has had an impact on the decline of matric results even though they affect the quality of teaching and learning inside classrooms. Department of social development spokeswoman Lumka Oliphant said it was possible that drugs caused poor academic performance.

"This is why the president appointed an inter-ministerial committee to address alcohol and drug abuse which includes the department of education.

"Drug dealers are targeting our school children. This is a problem throughout the country," she said.

Terrance Dzeli of Operation Thiba Nyaope, an organisation which looks after more than 1000 recovering addicts, agreed with the principals' concerns.

"The majority of young people on drugs are not doing well at school. We are inspired by the results attained by Gauteng, considering the fact that our province has a problem of drug abuse among youth," Dzeli said.

President of the National Professional Teachers' Organisation of South Africa Basil Manuel said the assumption that the pass rate dropped because of drugs was too wide.

The class of 2014 achieved 75.8%, down from 78.2% in 2013. - Additional reporting by Zoe Mahopo and Bongekile Macupe