South Africa's ranking as worst in the world for its maths and science education is "a state of emergency", the opposition has said.
The Democratic Alliance called for a full skills audit of all maths, science and technology teachers.
The World Economic Forum (WEF) report on information technology assessed the economies of 148 countries.
But the government has rejected it, saying the findings were based on perceptions and not hard data.
The World Economic Forum's The Global Information Technology Report assesses how ready countries are to exploit the opportunities offered by information and communications technology and how they can use it to improve conditions.
For the overall quality of education, South Africa came 146th in the WEF ranking.
While not all countries were surveyed, South Africa was ranked below Kenya, Nigeria and Zimbabwe.
Annette Lovemore, shadow minister for basic education, said her government counterpart, Angie Motshekga, should answer questions in parliament about the "worsening" state of education.
"It is deeply disturbing. Not only are we failing hundreds of thousands of learners in our schools but we are certainly failing our economy that needs the skills that maths and science produce," South Africa's Eyewitness News quotes Ms Lovemore as saying.
Ms Motshekga's Department of Basic Education dismissed the report as "based on interviews conducted with business sector executives".
"The WEF report does not base its research on any actual tests or assessments done by learners, they do not in any way interact with learners in the system or any credible education institutions to get their data," the statement said.
WEF world ranking: Quality of maths and science education
- Top five: Singapore; Finland; Belgium; Lebanon; Switzerland
- Bottom five: Honduras; Egypt; Dominican Republic; Angola; South Africa
"Credible international assessments into the state of mathematics, science and technology education in South Africa have consistently shown an improvement in the performance of the country in this regard," it said.
But Ms Lovemore said there had been no "false insinuation" in the report - and while there had been some improvements in recent years, the "overall picture is still frightening".
She said that 90% of 15-year-olds had failed to reach a "low level of achievement" in a 2003 world survey of maths and science - this figure was 76% in 2011.
"This is a state of emergency, and requires appropriate, urgent action," Ms Lovemore said.
The BBC's Pumza Fihlani in Johannesburg says last year a special ministerial task team investigated the teaching of maths, science and technology and painted a bleak picture of the country's education system.
Opposition parties accuse Ms Motshekga, who is serving a second term, of not doing enough to turn things around since the task team's report, she says.
The worst-affected schools are those in rural areas where a lack of teaching materials and teacher absenteeism are the major problems.