The UK has the sixth biggest classes in UKits primary schools, which are ranked sixth out of 34 nations on this measure.
See how Colorado's schools ranked below.
The ranks from "senior teacher in middle school" to "second-grade teacher in primary school" appear in decreasing order.
The average key stage 3 score of the secondary schools entered by Muslim children, for example, was only 94% of the rank of their primary school at KS2, while for Catholic children the equivalent figure was 102.8%.
Education was ranked according to five categories: no formal schooling, less than primary school, primary school completed, secondary/high school completed, and college completed or above.
Primary school pupils in Northern Ireland again showed remarkable maths prowess, holding the 2011 ranking of sixth overall, and the nation's exam results were the best in Europe among the 49 countries taking part.
For education, individuals were assigned an educational ranking that was either: no formal schooling; less than primary school; completion of primary school; completion of secondary school, or completion of high school or above.
The fact that Numeracy was ranked at the 6th place was surprising, given the importance given to mathematics in Singapore from primary school onwards (Berthelsen et al. 2011).
Girls out of school South Sudan ranks near the bottom among developing nations when it comes to primary school enrolment, with about 1.3 million children of primary school age out of school.
The village primary school.
