If not, a sequence of tests using a type of mathematics called modular arithmetic is carried out.

ECONOMIST: Number theory

In the new single level tests being piloted in English reading, English writing and mathematics, the questions are all pitched at a certain level of understanding.

BBC: All school Sats tests 'might go'

The OECD Programme for International Student Assessment or Pisa tests examines the performance of 15-year-old pupils in mathematics, science, and reading.

BBC: OECD asked by Leighton Andrews for Wales education review