Mexico has one of the highest rates of pre-primary school enrolment among OECD countries, but only under half of students complete secondary education, according to an OECD report in 2012.

BBC: Mexico's Pena Nieto enacts major education reform

Instead the authors recommend that "policymakers should concentrate on educational reforms in primary and pre-school" and want more effort made to raise the basic skills of disadvantaged groups.

BBC: Top maths pupils 'fail to keep up with world's best'

Unison said it would ballot its members in the pre-school, nursery, primary and secondary education sectors on industrial action in response to the cuts.

BBC: NEWS | UK | Northern Ireland | Board cuts lead to resignations

Most of them in a context of an expanded vision of basic education for all that should go from one year of pre-primary across to the lower secondary school cycle.

UNESCO: EDUCATION

Comparing the results of children who had been in pre-school classes and those who had not, the former pre-school pupils were seen to be more popular in all primary age ranges - with the most pronounced gap among 10 year olds.

BBC: Nursery children more popular