Timms, which analyses performance in maths and science at ages nine to 10 and 13-14, and Pirls which looks at reading among 10-year-olds.
BBC: Warning over world schools rankings
2.
The less expected success of the TIMSS and PIRLS rankings will be the high performance of Russia, which has a place in all their top 10s.
BBC: Asians top of school tables - England in maths top 10
3.
The global rankings are the result of two studies - the Trends in International Mathematics and Science Study (TIMSS) and the Progress in International Reading Literacy Study (PIRLS).
BBC: Northern Ireland is 'best in Europe' at primary maths