The survey revealed many teachers lacked confidence
Urgent action is needed to address "unacceptable failings" in maths and science in Scotland's schools, the education secretary has warned.
It comes after a survey of more than 60 countries and regions found Scottish pupils were below the global average.
The Trends in International Mathematics and Science Study (Timss) compared primary and secondary school standards.
It found only 51% of P5 pupils and 68% of S2 pupils were taught science by a teacher who felt "very well" prepared.
In maths, Scotland lagged behind countries such as Armenia and Slovenia - and its overall highest position was 13th out of 49 countries.
Education Secretary Fiona Hyslop has demanded a detailed analysis of the report is put together for a summit in the new year.
She said: "This survey highlights unacceptable failings in maths and science in Scotland's schools and confirms the urgent need to act.
"During the last administration the achievement of Scots pupils fell back between 2003 and 2007 compared to other countries.
"There is no doubt this government has inherited a great challenge and it is for us now to take action. This survey paints a picture of Scotland standing still while other nations pushed by."
Compiled by researchers in the US, the Timss study is an important benchmark for comparing standards in maths and science around the world.
Nearly 4,000 P5 pupils and the same number of S2 pupils took part.
As in 2003, the best results have been achieved by Pacific rim countries, such as Singapore, Hong Kong, Chinese Taipei and South Korea.
England's pupils were placed in the top 10 for science and maths.
Scottish Conservative education spokeswoman Liz Smith said the findings were "alarming".
She said: "This survey paints a very disappointing picture.
"I am particularly concerned about the lack of basic skills in mathematics which, together with the issues about basic literacy amongst too high a proportion of the pupil population, re-enforces the need for far more focus to be put on the teaching of the 3Rs at primary school."
Margaret Smith, the Liberal Democrat education spokeswoman, said that changes in the qualification system in Scottish secondary schools would not address the problem.
She said: "The government's recent announcement on a Scottish baccalaureate focusing on sciences was muddled and weak on detail.
"It will do little to reassure parents and teachers that ministers are taking unacceptable figures like these seriously."
Labour's schools spokesman Ken Macintosh said: "It is clear that the particular difficulties with science and maths must be addressed by the Scottish Government.
"What's more, the lack of funding for science departments at university level and the lack of clarity over science in the curriculum for excellence is all the more worrying."