declining birth rates for example may drive down the demand for new teachers and longer tertiary education can delay the entrance of teachers to the labour market the ageing of teachers increases school costs which limits the resources available to implement other initiatives at the school level oecd education at a glance indicator d the proportion is equal or more than in the czech republic estonia hungary the netherlands portugal and the slovak republic at the other end of the spectrum in most countries with available data of preprimary teachers are under the age of only in australia korea japan new zealand turkey and the united kingdom does the proportion of preprimary teachers under the age of equal or exceed figure