Half of developed countries are worried about attracting and keeping high-quality graduates in teaching, particularly high achievers, men, and maths and science graduates, according to a report for the Organisation for Economic Co-operation and Development.
The findings were presented at an OECD conference, Teachers Matter, held in Amsterdam last week.
Teacher quality has become a new focus of international attention. The OECD's 2002 Pisa study, which compared literacy and numeracy levels of pupils in more than 40 countries, showed that in Germany, Greece, the UK, and the Nordic countries two out of three 15-year-olds are in schools where headteachers believe learning is hampered by teacher shortage or inadequacy.
Students of the top 20 per cent of teachers have learning gains four times greater than those of the lowest 20 per cent, a 10-year study of American 12 to 16-year-olds found. Similarly, "having a succession of effective teachers can substantially narrow the average achievement gap between students from low-income and high-income families", says the soon-to-be published study Teachers matter: Attracting developing and retaining effective teachers.
While student ability, attitude and background has the largest impact on performance, teacher quality has emerged as the single most important factor affecting pupil achievement.
Quality is defined by more than teacher qualifications, academic ability and experience. Key factors include enthusiasm, creativity, and the ability to convey ideas.
At the same time teachers' jobs have changed. Society now expects schools to deal with children from diverse backgrounds, to be sensitive to culture and gender, to promote tolerance, to respond well to students who are disadvantaged or have learning or behavioural difficulties, to use new technologies and prepare students for lifelong learning.
Teachers also need social and managerial skills. Leadership and organisation is required to build up a partnership between schools and for international co-operation.
They must be able to use data and adjust their teaching accordingly. "In the past, there was very little exposure to assessment for teachers," said Phillip McKenzie, the report's co-ordinator.
Studies show effective teachers are intellectually capable, articulate, knowledgeable and able to think, communicate and plan systematically.
Students achieve more with teachers who perform well on tests of literacy and verbal ability.
"The attributes for effective teaching may only become evident once they are working," Mr McKenzie said. "It is difficult to know in advance who will be a good teacher."